The Government s "Cash for Clunkers" program may be history, but the idea lives on.

The Department of Energy recently launched a Cash for Refrigerators program to encourage consumers to replace their old appliances with new, energy-efficient ones. Babies R Us now offers a 20% discount on cribs, strollers and other pieces of baby gear to customers who bring in used ones.

Other retailers will pay you cash for your unwanted books, CDs, DVDs and old and broken iPods -- without requiring you to purchase new ones.

However, unlike the government-run programs or in-store promotions, most of these services operate exclusively online. Consumers are required to mail in their items and then must wait to be paid by check or PayPal deposit. The draw is the convenience. For example, rather than lug your books to a used-book store, you can bring them to the nearest post office or FedEx (FDX) drop-off location. And with most services, mailing charges are paid by the retailer.

Of course, any business transaction conducted through the mail and on good faith comes with risks. You may have been quoted a certain price for your stuff, but if the business deems your description inaccurate, that quote may change. Or they may reject your items altogether and discard them unless you cover the return shipping costs. And because these are all for-profit ventures that resell your items and pay for your shipping costs to them, they re likely to offer you a lower price than you may get dealing directly with a buyer on eBay (EBAY) or Craigslist.

Still, if you re looking for a no-hassle way to clean out your bookshelves or entertainment center, these services may be worth a try. Just be sure to vet a company before putting your stuff in the mail. Check its Better Business Bureau rating: Anything lower than an A or B grade should raise a flag, says Michael Galvin, a spokesman for the BBB of Southeast Florida and the Caribbean. If that s the case, call the local BBB and find out why that is. The branch can tell you if there s a pattern of complaints about the business and point out other concerns. If there are registered complaints, check whether they have been resolved.

And before you send in your stuff, get an idea of what it s worth and how it compares to the company s quote. The easiest way to do that is to check the selling prices of similar items on eBay, says Doug Norwine, the director of music and entertainment memorabilia at Dallas-based Heritage Auction Galleries.

Here are three businesses to consider:

1. Books

Run by Beaverton, Ore.-based McKenzie Books, Cash4Books.net will pay you between 57 cents and $120 per used book. How much you get depends on the book s weight and retail value, how quickly it is expected to sell and how many copies are already in the company s warehouse, says Crystalin Tadano, a senior customer service representative at the company. The firm specializes in college textbooks and technical books, which are more likely to pay top dollar than, say, paperback novels.

On average, sellers get around $20 per book, according to Tadano, though a recent check by SmartMoney.com yielded lower results. The personal finance and investing books we ran through the Cash4Books.net system would fetch around $5 at best (we were quoted $4.59 for The Progressive Discipline Handbook: Smart Strategies for Coaching Employees (with CD Rom) by Margaret Mader-Clark and Lisa Guerin). Getting an online quote is easy: Just enter the book s ISBN number.

The perks: Shipping is paid by Cash4Books. You get free FedEx shipping if you sell five or more books. You can get paid by check or PayPal. If you choose the latter, you get a 3% bonus to offset the Paypal fees.

The fine print: Cash4Books will not accept books with tears to the cover or pages, major wear to the binding, missing or loose pages, water or other damage, and strong odor. Writing, underlining or highlighting is OK as long as it appears to be on fewer than 20% of the book s pages, but it may result in a reduction of the quoted price. If not accepted, McKenzie will ship books back only at your own expense.

Due diligence: The Better Business Bureau has registered nine consumer complaints about Cash4Books.net over the past 36 months. All have been resolved. The company has an A rating.

Old CDs, DVDs and games gathering dust on your shelves? Santa Barbara, Calif.-based Morninglory Music, which runs CashforCDs.com, will pay you between $1 and $3 per CD and DVD, and between $3 and $5 for each PlayStation, Xbox or Wii game, says Stan Bernstein, the company s owner. How much you get depends on the title and the condition of the disc.

The average customer gets between $4 and $20 for six CDs (the minimum number of discs you have to ship to participate). Our experience was pretty much in line with that estimate: We were quoted $20 for two CDs, one DVD and three games (one each for PS2, Wii and Xbox), each in good or excellent condition. But we did strike out on the six other CDs we checked out, which included INXS s 1990 album X and Pearl Jam s Ten from 1991.

CashforCDs.com isn t currently buying them. Bernstein says there is an oversupply of certain CDs and not much demand on the marketplace -- a trend that isn t likely to reverse.

The perks: You don t need the cases. The company will send you a paid-postage mailer for the CDs and front and back covers.

The fine print: For copyright purposes, the company requires the front and the back cover of each CD, DVD or game.

Due diligence: Morninglory Music is rated A+ by the Better Business Bureau. It had one complaint within the last 36 months, and it has been resolved.

3. iPhones, iPods and other small electronics

Don t just toss away your old or broken iPod, Zune or iPhone. Kalamazoo, Mich.-based RapidRepair.com will be happy to pay you for it. The company, which has been in business since 2004, specializes in repairing small electronics but also buys them from consumers to use for spare parts or repair and resell as refurbished. How much you get for your unwanted gadget depends on its model and condition. You may get anywhere from $20 to $50 for an old iPod with a broken screen, if the device or its spare parts are in demand, says Ben Levy, the company s owner. An iPhone 3G can fetch up to $200.

The perks: You can get cash for an item that you can t otherwise sell or repair.

The fine print: RapidRepair.com doesn t accept gadgets with liquid damage -- a diagnosis few users can pronounce on their own -- so you may end up sending in an iPod and getting nothing in return. Postage is paid by the seller, though given the size of the items, the cost is fairly low.

Due diligence: The company has an A rating with the BBB. All five complaints filed against the firm in the last 36 months have been resolved.