Bush's present to the American people is on its way. Some lucky tax payers already got their tax rebate check yesterday. The tax rebate is also called Economic Stimulus payment. What that implies is you should spend the $600 as fast as possible. One way to do that very quickly is to treat yourself to a new cool gadget.

If you are a family, say with two kids ($1,800) you actually get enough for a decent full HD HDTV.

With $600 you are actually a bit limited on what cool gadget you can get. You can spend it all on the 16GB iPhone. You still have $101 left to burn on the monthly contract fees. You could also go for the 32GB iPod Touch that also sells for $499. With the remaining $101 you can go crazy on iTunes.
Either way spend it wisely or invest it in stocks. You can get one Google share and three Apple shares...

More details on the IRS site.