Here's what to do, taken straight from androidcentral:
Open the Android Market and search for a terminal client. There's several free ones, and they all work great. If I was forced to recommend one, I would choose Connectbot, but any of them will work.
Open the terminal app, read through the instructions (if any) you see, and you'll be faced with a text entry prompt. If your prompt is the pound sign ( # ) -- you're rooted. If you see a dollar sign ( $ ), try entering the command "su" (without the quote marks). You might see a dialog asking for permission from the SuperUser app, which you can safely grant. If the prompt changes to the pound sign, you're rooted.