A friend of mine uses Tracfone and he likes it. However, I think I get at least as good a deal with T-Mobile. I pay $25 for 100 minutes that are good for 90 days and that roll over as long as you keep the account activated. After paying a total of $250 for minutes (which will take me about 2.5 years at the pace I'm going) you hit "gold status" and then get a bonus 50 minutes with each $25 minute purchase for a total of 150 minutes. If you want more minutes at a time then it is cheaper per minute - $50 for 250 minutes (375 after gold status) or $100 for 665 minutes (1000 after gold status).
I'm not sure what the phone selection is like with Tracfone but with T-Mobile I get a pretty big selection. I've got a small Motorolla phone which is tri-band GSM (means that I can use it in other countries), T-Mobile will unlock the phone after 90 days (means that I can take it to other carriers even in other countries if I wish - good for trips - buy a SIM card), the phone connects up to my computer and I download my address book with all my phone numbers, etc.