Even the most organised people have a hard time sifting through a giant downloads folder trying to find that one file -- especially if you don't know what the file's name is. Sort your downloads folder by date to solve this problem.
This isn't something everyone will need, but it's something I've found immensely useful lately. When I download a file (via BitTorrent, especially), I don't know what the file name is, which makes finding it difficult. So, I've started sorting my Downloads folder by "Date Created". That way, the file I just downloaded is always at the top of the list -- no searching or scrolling needed. Note: in Windows, you may have to create this column by right-clicking on the sorting headers.
If you keep your Downloads folder clean, this won't be necessary, but for heavy torrenters (or those that seed everything they download), it's convenient.