Three neat little freeware apps that get a thumbs up:
TreeSize: "Every hard disk is too small if you just wait long enough. TreeSize tells you where precious space has gone to. TreeSize can be started from the context menu of a folder or drive and shows you the size of this folder, including its subfolders. You can expand this folder in Explorer-like style and you will see the size of every subfolder. Scanning is done in a thread, so you can already see results while TreeSize is working. The space, which is wasted by the file system can be displayed and the results can be printed in a report."
Basically, just a very handy tool to see which folders are eating space. :)
BitComet: The name gives you a hint - it's a BitTorrent client. I was previously using G3 Torrent, which admittedly looks much nicer than BitComet. The difference is that BC is UPnP-aware, meaning that I don't need to forward ports on my router. They're opened and closed dynamically, as necessary. This is a feature of Azureus too, but BC is coded in C++ as opposed to Java, and it feels snappier.
Ava Find: Saved the best for last. In short, this is a superb, superb app that I think every Windows user should install and use. I tried AppRocket about half a year ago, and I really liked how efficient it made opening and searching files, but I wanted a freeware solution. Ava Find was the answer. It makes searching for
any file on your drives
instantaneous. You just have to download it and try it to see how nice it is.
NOTE: This one isn't exactly freeware since some features get disabled after 30 days, but the essential functionality continues to remain after it expires.
UPDATE: Forgot to mention - use the keyboard shortcuts in Ava Find. Much more convenient. Shift+Esc to bring it up, Esc to hide it again. :)