Java Developer's Alamanac online
I downloaded the example code from the Java Developer's Alamanac years ago when it was on Sun's Java website, and it's great. I still use it every time I start messing with a class I haven't played with before. I just found a link (from Karl's paradox1x) to the newest version, that's now online in searchable format. It's not as nice as having all the files locally, because you can't copy and paste right in the same editor, or compile the code and play with it right there, but it's still pretty cool.
-Russ