Leopard introduced the ability to use the Spotlight as a simple calculator. But, if you wanted to use exponentiation, you had to type something like pow(2, 3).
In Snow Leopard this has changed. pow no longer works, but you can instead just type 2^3, and Spotlight will display 8.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090911091954765