I used Virgin Mobile happily for a while, and they are the best if you're happy with limited minutes. Virgin Mobile's plans are restarted each month, and they offer unlimited text, unlimited data, and 300 minutes for $35, which is phenomenal; however, 300 minutes isn't going to be enough for most people. Their next plan is $45/month, which gets you up to 1,200 minutes; at this point you're paying $45, so you might as well be using Straight Talk, which is $45/month for unlimited talk, text, and data.
One very cool thing about Straight Talk is that using this provider gives you the option to have practically any phone you want, because of their "Bring Your Own Phone" program. Any GSM (meaning uses a SIM card) phone that is unlocked, T-Mobile, or AT&T (or a Straight Talk phone, of course) will work with Straight Talk. Regarding how good coverage will be for these phones: Straight Talk or unlocked phones use Verizon's prepaid towers, while AT&T or T-Mobile phones through Straight Talk use the AT&T or T-Mobile towers. That means your coverage is premium... the same coverage as if you were using the providers directly. Like Virgin Mobile, Straight Talk is prepaid, so every month (unless you pay for multiple months at once) you restart your plan.
So Straight Talk offers $45/month for unlimited everything, and the widest phone selection you'll find anywhere -- do you know of a better carrier?