Sometimes I'd remember this awesome thing that I saw on Reddit awhile back and want to share it with someone. I'd try to find it through browser history or reddit search, but I wasn't usually successful. Reddit search isn't very good and I use Reddit a lot so my browser history for reddit.com is huge and unwieldy.
So in my spare time I decided to write Reddit History. It basically just keeps track of all the submissions you've viewed, and lets you filter them by sub-reddit and text search (regex).