SubtitleSplit is a web-based tool for not only searching out subtitles but also "fixing" subtitles through various actions like synchronisation, splitting and merging.
Subtitles are great and when you're lucky you find a perfect match — if you've never downloaded subtitles before, you don't know the bliss of loading a perfectly synced file, no tweaking required. When you're not lucky the subtitles were made for a different copy of the file you're using, the syncing is off because of poor syncing in the container file, and so on.
Over at SubtitleSync they've combined the act of looking for subtitles with fixing them. You can search for subtitles that fit your file and if the fit isn't perfect you can kick the subtitle file over to the SubtitleSync editing tools. You can synchronise a file to adjust the playback time, split it if you need to break apart the subtitles to fit multiple chunks of one movie or show, merge them together for the opposite need, and then share your repairs subtitles with the greater community so another user doesn't have to go through the same work you just did.
SubtitleSync is a free service and requires no download. Have a favourite subtitle tool — web-based or otherwise? — let's hear about it in the comments.