I found this little gem last night while I was supposed to be sleeping - the Name Voyager. It's this totally rad little flash applet that shows how popular individual names were by decade. The wider the band, the higher that name was ranked for that particular decade. You can run your mouse over the whole graph to highlight individual names, or type in a name (or first few letters of a name) that you're interested in to get more specific.
Looking through it made me try to figure out the reasons for the trends, like why some names are incredibly popular for a decade or two and then completely drop off. Check out "Betty." Betty was the ranked 44 in the 1920's and then hit number 2 in the 1930's. By the 60's it went back down to 104. Why? Betty Grable? Or how about the names that come out of nowhere, like Jennifer. Jennifer wasn't even ranked in the top 1000 before the 1940s and then all of a sudden by the 1970's it's the number one girl's name. Where did that come from?
Anyway, it's kind of cool to look at, especially if you're currently considering names.