We live in the country, and our cell phone coverage is iffy, at best. However, we didn't want to put an expensive long-distance calling plan onto our land line so we purchased am AT&T calling card from Sam's Club. This works perfectly for our needs.
Calls are much cheaper than with a regular long-distance plan, especially if you don't use that many minutes each month (which can be the case if you have a cell phone). Cards come with different numbers of minutes on them and the more minutes you purchase, the less it costs per minute.
You can use these easily anywhere you go. When visiting friends and relatives, I can make long distance calls on their phone and not have it be charged to their bill.
These are easily re-charged. At the beginning of each call you will be informed of how many minutes you have remaining. If you begin to run low, there is an option to add more minutes with your credit card. I've done this several times and it doesn't cost any more than you paid for the initial card.
You have to dial a 1-800 number, then dial a 16 digit access code, THEN the phone number you want to dial. This can take a while, and if you mess up any of these, it can take even longer.
You are charged extra minutes if you use these at a pay phone, or in a foreign country.
Overall I highly recommend these. I personally think everyone should have a calling card to begin with in case of an emergency. The AT&T card from Sam's is a nice one to have.