I've lived/worked in a LOT of cities in the USA (as well as another country). If you're an IT researcher, USA is probably the place to be for the greatest earning potential/mobility -- this is where the brainpower of the world aggregates. It will continue to be this way for a while despite reports to the contrary.
Food, gas, and electronics are cheap and plentiful. People (depending on where you are) have a high tolerance for eccentricity, 'different-ness', and new ideas. The Internet (for the time being) remains uncensored.
Seattle is EXCELLENT for jobs (even if you don't want to work for Microsoft), and has both a hacker and a foreigner friendly culture. This is the only place I've ever been where I can put a resume online and get around 8 phone calls the same day (YMMV). Besides Microsoft, it has Amazon, Boeing, and a couple of other places you've heard of nearby. That being said, it can be very isolating, and very cold and dark if you're from Southern Europe. The cost of living is high, but not insanely high. The city is beautiful and eclectic (live in the city -- do not move to Redmond -- neither beautiful nor eclectic!). It's the perfect place to be in the summer, and wonderful in the winter if you like having ski resorts within 30 minutes of driving distance. Avoid anyplace in this latitude if you have a problem with 4:30 pm sunsets during the winter.
Silicon Valley is another place where you will probably find a good critical mass of companies who need your skills.
Los Angeles is a place that I'd personally like to move to, and I imagine would have critical mass. The weather and beaches are beautiful.
The Washington, DC area (East Coast in the USA) including Northern Virginia and Southern Maryland is also a good area for IT, but has a lot of defense contracting work (which means that you will be at a disadvantage as an immigrant).
Florida also has some decent opportunities, and the wonderful bonus of being able to drive to the beach whenever you want (you will miss this pretty much anywhere else in the USA, even if it looks close to the water on the map).
Texas is also rich and foreigner-friendly in a way that you would not expect -- but it's not Silicon Valley!
I would stay away from the Midwest (as wonderful as it is) and any metropolitan area whose name you've never heard of, even if the particular opportunity is good. You will want the ability to change companies without necessarily moving.
Another piece of advice: If you care at all about your home country, do three things: 1) try to find a position that will let you go to there for the summers -- e.g., an appointment at an institution for only 9 months, etc. This is very difficult to come by, but otherwise you may be slowly driven insane with homesickness and the one to three (if you're super-lucky) weeks of vacation that a typical US company will give you. 2) Get plugged into your local expat community. Make sure it exists where you're going. 3) Pick a place with the most direct airline routes back to your home city -- otherwise you'll waste 2-3 days traveling each way (I'm not kidding!).