One of my favorite pieces of software that died while trying the Extreme Sport of transitioning from DOS to Windows was Magellan. It was a file manager for DOS that indexed your hard drive, then showed you the results in a list. Searching for some phrase that was on your drive was instantaneous. Now, you can get the same thing with Google Desktop. My only complaint is that you can't tell it what types of files you want it to index -- it defaults to things like Office documents and emails. But, lo and behold, there is a plug-in API. And someone has written a Google desktop plug-in that indexes Java source files. Plug it in, let it trundle a while to build the index, and you have instant access to interesting stuff you have in your Java files. Great for spelunking around a deep and wide object hierarchy. Because it's indexed, it's as fast as Ctnl-N in IntelliJ for finding classes, but it works over the entire file system, even on really large drives.
It indexes on the fly (it's amazing how fast it picks up new files), waiting on CPU idle time to kick in. The indexes on my machine currently take up about 1.5% of the disk. It changes the way you search for things, though...I'll give up 2% of my hard drive to get instant access to needles in a 30+ GB haystack.