You can tag any file (or group of files) by dragging it onto the tag2find TagBox, then typing the tag(s) you want to add, or through the right-click context menu. In order to encourage you to tag new files as they're created, tag2find can also monitor your new files and prompt you for tags. tag2find then provides a couple of ways to search through your tags, both of which seem to provide snappy results. Add to that automated tagging by filetypes, tag clouds, and Windows Media Player integration, and tag2find is a surprisingly powerful tool.
tag2find [via lifehack.org]
More...