UPDATE: ZebraGSM looks to be a scam. Ech.
As spotted by The Sweeper over on the Go4Prepaid forums, it looks as though we have another MVNO that's both unlimited and GSM. This time the name is ZebraGSM, and the prices are good enough that the outfit should be out of business in about six months...
The plans are good though, so you may want to check them out if you're in ZebraGSM's signup-for-service area, which includes 25 states on teh east and west coasts...
$39.99 - Unlimited local/long distance/calling features (Caller ID, call waiting, 3-way calling, etc.)
$49.99 - $39.99 plan plus unlimited text
$59.99 - $49.99 plan plus unlimited MMS
$69.99 - $59.99 plan plus unlimited web
Family plans are $20 per month extra per line, no matter what plan you add them to.
Phone selection is pretty good, though prices are nowhere to be found. This is because, like many such providers, ZebraGSM farms out sales to dealers. But here's the list (all made by Motorola, interestingly):
SIM-only (good if you have an unlocked 850/1900-capable GSM phone you want to use on the service)
c168i (okay basic phone)
w215 (basic phone with camera, haven't seen before)
v220 (camera flip phone)
L6i (SLVR but cheaper)
Rokr e1 (nothing to see here, move along...no, seriously0
Razr v3 (party like it's 2005)
Rizr z3 (the Razr, spiffed up slider-style0
Note: "unlimited" isn't exactly unlimited here, but for most purposes you're okay here. Minute usage is capped at 10,000 per month, Texts are capped at 30,000 per month, and data is (you guessed it) 5GB per month. Unless you're using your phone as a modem, you should be good to go. Until these guys go out of business, that is...
Still, really good plans while they last. Looks like they're using AT&T's network by the way, so coverage should be good.