Are you fed up with the nickel-and-diming big four carriers of the U.S.? There are alternative options out there for prepaid and they usually work out pretty well if you're interested in a smartphone. One such choice you could try is Walmart's Straight Talk which offers unlimited everything for as low as $45 a month. Not a shabby deal but the phones they offer for sale are, frankly, horrendous.
Fortunately for Straight Talk users there's a thread over at XDA-Developers Forum to help you get an unlocked Samsung Focus (or Omnia 7) up and running at full capability (including Internet Sharing) with the pay-as-you-go carrier. Thread author fatclue points out that they are a GSM-based carrier which means you can just pop in a Straight Talk SIM card into any unlocked AT&T or global-ready smartphone and be on your way...except for one little problem. MMS won't work without some extra hacking.
It's a little complicated as it requires some registry editing on the phone and deployment of a xap file containing the info, so if you don't need MMS it may not be worth the trouble. But if it's something you're interested in then you should check out the source link below (Note: as far as we can tell, the files are meant for the Focus/Omnia 7 only). Also if you're looking for a place to purchase an unlocked Samsung Focus the best price we've seen is from a seller on Amazon for $229. Good luck!
Source: XDA-Developers Forums