Much like dial-up Internet service or the recently defunct web hosting service GeoCities, telephone landlines could be turning into 20th century relics.

In the second half of 2008, 20.2% of American homes had at least one cellphone but no landline, up 2.7% from the first half of that year, according to the National Health Interview Survey (NHIS) conducted by the Centers for Disease Control and Prevention. That was the largest six-month increase since the agency began collecting data in 2003. The report also said that 14.5% of households with cellphones and landlines received all or nearly all their calls on a cellphone. (The NHIS collects information on health status and household phones.)

Although data suggest that wireless-only households are slowly becoming the norm, some consumers are reluctant to ditch their home phones altogether. Some are concerned about wireless service outages. Others want to avoid dropped calls. And some just like the feel of a traditional receiver.

But many callers who refuse to part with their landlines face higher costs to call outside their local area. Consumers can either pay for that service by the minute or subscribe to a plan that includes local and long-distance calls. And many callers with landlines are paying extra for the ability to make long-distance calls regardless of how often they make them.

Here are three options for customers looking to save on long-distance calls while keeping their landline.

1. Use your cellphone for non-local calls

The simplest way to save on long-distance calls is to strip out long-distance service from a landline and make those calls on a cellphone instead. Most cell plans include long-distance (national) calls in their minute usage limits, so making those calls is effectively free provided the user doesn t exceed his or her limit.

Calls abroad are another story. Using a cellphone to make international calls is expensive and is usually an a la carte service (the caller is charged per minute), says Allan Keiter, president of MyRatePlan.com, a site that compares wireless and home phone plans.

It is possible to mitigate those costs by adding an international service. For example, for AT&T Wireless customers who add AT&T World Connect to their plans, calls to Germany are nine cents a minute to a landline and 26 cents to a mobile phone. The international package includes $3.99 monthly charge. Otherwise, standard rates apply: Calls are $1.49 and $1.66 a minute, respectively, without a monthly fee.

2. Get invited to Google Voice

Google launched its phone service, Google Voice, earlier this year. The service allows users to funnel all of their calls through a single phone number that forwards to an office, home or cellphone. Last week, Google announced the service could be used with existing cellphone numbers instead of having to obtain a new number from Google. (Using Google Voice with an existing number excludes some features, like call screening and recording, but includes others like Google voicemail, which allows users to listen to voicemail on their phone or computer or read it as text messages.)

For long-distance users, all calls to U.S. locations (except Hawaii and Alaska) and Canada are free (if you re using a cellphone, they count toward plan minutes). However, frequent international callers might not find Google Voice as cost-effective as other services, notably Voice over Internet Protocol, or VoIP, says Schwark Satyavolu, president and co-founder of BillShrink.com, a web service that compares cellphone plans.

Rates for calling abroad vary based on the country and whether the call is to a landline or mobile phone.

Right now, Google Voice is available by invitation only. Those interested can request an invitation here or ask a friend with a Google Voice account to send them one.

3. Use a VoIP service

Another strategy for those attached to their landlines is to keep a basic, no-frills phone service (no call waiting, no long distance) at a cost of about $10 to $12 a month and make outgoing calls using a VoIP service.

The offer requires a one-year agreement

Using the Vonage package, consumers could keep their landline to accept calls or faxes and reliably make 911 calls. But it could serve as more of a secondary line with the VoIP service as the primary line.

Skype is another VoIP service consumers have long used to save on long-distance calls. It s a free downloadable software application for your computer. Plug in any headset and you can call other Skype users around the world for free. Calls abroad (to a landline or mobile phone without Skype) start at 2.1 cents a minute and vary based on where you re calling. (Generally, calling a landline is less expensive than calling a mobile phone.)