As colleges have struggled with belt-tightening in the downturn, they ve been getting a helping hand, albeit a small one, from a surprising source: Grandma and Grandpa.

Although colleges have laid off nonacademic personnel and suspended retirement contributions in the last two years, in most cases, they haven t cut not-for-credit courses offered to retirees. That s because retirees typically add to a school s revenue auditing a course can cost from $25 to $500 per semester depending on the college without contributing to overhead costs. At the University of Denver, for example, revenue from one of two programs geared toward retirees runs about $360,000 annually.

Each school s offerings and charges for retirees will of course vary. In general, the Ivy Leagues will be more expensive, says Roland King, a spokesman for the National Association of Independent Colleges and Universities, which represents 900 private colleges and universities. If Ivy Leagues open their doors free of charge to all, they re much more likely to be overrun than a small liberal arts college, he says.

There are also state and national programs geared toward affordable retiree education. In Ohio, public universities, like Ohio State University and University of Toledo, offer what s called Program 60, which permits individuals who are at least age 60 to attend classes for free. Meanwhile, more 115 colleges are members of the Ocher Lifelong Learning Institute, a noncredit educational program developed for adults who are age 50 and older; prices vary depending on the institution.

Here are eight colleges educational noncredit offerings for retirees.

1. Yale University

Location: New Haven, Conn.

Yale permits only its own alumni and their spouses to audit courses as well as certain members of its faculty and staff, says Kathryn Young, the director of Yale Summer Sessions & Special Programs. That s because the university regards auditing as a benefit given to those within the Yale community, she says.

Retirees who graduated from Yale can audit undergraduate courses (but not graduate courses) as long as the professor approves. Auditors are usually limited to lecture courses; smaller classes are harder to get into. It costs $475 for one course per semester. That s up from $460 from the 2008-09 academic year.

2. Cornell University

Location: Ithaca, N.Y.

At Cornell, retirees can sit in on most undergraduate and graduate courses, which cost $101 per credit around 90% off the regular tuition price. Most classes range from one to four credits each. (Smaller workshop courses Cornell classifies as participatory are excluded.) The university also offers retirees the option of taking non-credit classes taught by the university s professors. In the summer, there are four one-week session classes beginning on July 11 that cost $895. Class topics to choose from include natural history, ethics, politics, tennis, landscape painting and bronze casting.

Throughout the year, the university hosts study tours that range from one- to three-week long trips where professors teach a specific subject. From Feb. 20 through Feb. 25, participating students will visit the Florida Keys and Everglades for a course on natural history and the habitats of southern Florida. The price: $2,995 per person for double room occupancy airfare not included.

There are also weekend seminars where two Cornell professors accompany a group on a nearby trip to discuss timely issues. For example, during Oct. 29-31, a series of lectures and discussions will be held in upstate New York regarding midterm elections. Cost: $1,255 including lodging and meals. Click here for more information.

Location: Philadelphia

UPenn offers a senior auditing program for individuals who are age 65 and older where they can follow undergraduate lecture courses (excluding language classes, labs and seminars). This list is prepared for us by the college based on space, undergraduate student enrollment and other factors, says Chris Pastore, program director of the Master of Liberal Arts program at UPenn s College of Liberal and Professional Studies.

Pastore says retirees cannot audit classes that require participation, like labs or seminars. Senior auditing is primarily designed to let the program students come and listen to lectures, he says. Also, retirees can take up to two classes per semester. The university charges $500 per course (up from $180 in 2006).

4. Princeton University

Location: Princeton, N.J.

Princeton permits retirees to sit in on most undergraduate courses there are typically 200 per semester to choose from through its community auditing program, which is open to adults of most ages.

The first day of registration is open only to Princeton residents; after that, the university doesn t have specific geographical requirements for auditors. We say the program is for adults who live within reasonable commuting distance from the university, says Emily Aronson, a spokeswoman for Princeton. (It s up to the students to determine what that is, she says.)

The cost is $125 per course, compared with $50 per course in 1999 when the program started. As community interest in the program has increased, staff resources to administer the program were increased accordingly, and the cost helps cover the administrative resources needed to run the program, says Aronson.

5. Babson College

Location: Wellesley, Mass.

Unlike the Ivy Leagues, this New England-based private college is more affordable for retirees. In fact, auditing undergraduate classes is free. To attend, retirees must be at least age 65 and reside in the towns of Wellesley or Needham. Auditors can take one class per semester with no limit to the number of semesters they enroll.

Starting this semester, the university also permits auditors to sit in on graduate courses, says Carolyn Place, assistant registrar at Babson College. Auditing has always been free. We do it as a benefit to the community, she says.

Location: Denver

This university gives retirees two options for participating in classes. Its senior citizen audit program allows adults age 60 or older to audit select undergraduate classes. Availability is based on class size and receiving permission from the professor, says Kim DeVigil, spokeswoman for the university. It costs $25 per course, but auditors aren t eligible to check out library books or to use the school s athletic facilities.

The university also features the Osher Lifelong Learning Institute, which is open to individuals who are at least 50 years old. Qualifying students can enroll is as many classes as they d like, and the membership fee is $100 a session the same as it's been since 1996. (The university runs on a quarter system, not semesters.) These classes are specifically tailored to older adults and topics include art, dance, film, health care, politics and foreign policy.

7. San Diego State University

Location: San Diego

San Diego State University also features the Osher Lifelong Learning Institute, which permits individuals who are at least age 50 to take classes on campus. At San Diego State, there s an annual fee of $35 the price remains unchanged since the university started offering this program in 2004 for single students and $50 for couples.

Students can take as many classes as they d like; currently the university is offering 30 classes in this program on topics including philosophy of religion, Shakespeare and Iran. This program emphasizes the fact that these people never want to stop learning, says Steve Dolan, a spokesman for San Diego State University s College of Extended Studies, which administers the program. Instructors include San Diego State professors, former professors and retired Burger King CEO Jeff Campbell.

8. Ohio State University

Location: Columbus, Ohio

At Ohio State University, Ohio residents who are at least 60 are permitted to audit undergraduate and graduate courses for free in accordance with the state-mandated Program 60.

At OSU, most classes are available to people age 60 and up assuming there is class availability and instructor approval, says Diane Dortmund, a program coordinator at Office of Continuing Education at OSU. (Courses excluded from the program include medical classes, aviation classes and core classes that are part of the Masters of Business Administration degree.) Tuition-paying students always have priority, and if the instructor feels there is room for more students in a course, he ll include retirees, she says.

Edward Sadar, a 66-year-old retired neurosurgeon, enrolled in OSU s Program 60 from 2006 through 2009 to brush up on his Spanish-speaking skills. I ve always enjoyed languages, and I took Spanish in college. When I retired, I decided I had the opportunity to become more fluent, he says. Now, he says he uses his language skills when visiting his daughter in Spain and when he volunteers at a Columbus-based physicians clinic where half of the patients are primary Spanish speakers.

There is no limit on the number of students the program accepts. The incentive for retirees is lifelong learning and personal enrichment, says Dortmund. Some people prefer to talk about intellectual topics rather than the daily humdrum in senior circles; it keeps the brain active.

An earlier version of this article stated that retirees are not permitted to sit in on undergraduate courses at Cornell. They may sit in on most undergraduate and graduate courses for a per-credit fee.