While the Galaxy S II has already made an appearance at Samsung USA's website, the handset hasn't been officially released Stateside yet. However, if you want to buy it before any carrier gets the chance to launch it, you can do it now thanks to Newegg. The retailer is selling the Samsung Galaxy S II unlocked for $649.99. This particular version that's available at Newegg has 16GB of internal memory, and comes with quad-band GSM (850x900x1800x1900) and quad-band UMTS (850x900x1900x2100) connectivity – hence it's compatible with AT&T's and T-Mobile's networks (although you'll have 3G only on AT&T).
Unwired View, Samsung Galaxy S II available in the US (unlocked, but will work on AT&T and T-Mobile)