I've been giving a lot of thought to something new for my website.
It would be nice to have tagged notes, and be able to search them as easily as finding a webpage on Google. Maybe a double row of tags at the top. One row for your friends posts. One row with tags you like to read, new ones noted, easily scrolled. Add a tag from the tabbed list, remove another... With jQueryUI, it's easy to make sub-windows that are draggable and resizable. How about editable and tag-able as well?
How about a hyper-link that end up at a table of search results for various posts, in order made with titles etc. Filter out any tagged #nsfw or filter just for those. So many unimplemented possibilities, but which is the next Big Thing?