For anyone who's been interested but who prefers completed works, Homestuck is finally coming to an end on the 13th. If you start reading now you'll probably catch up sometime after it's done. If you haven't heard of it, it's a long and increasingly epic comedy/action/sci-fi/drama web-comic/multimedia-extravaganza with an interesting setting and a huge cast of characters, with a fanbase ranging from hordes of teenage girls to Eliezer Yudkowsky. Definitely not for everyone though. Helps if you can enjoy irreverent humour.

edit: If you do start reading, it may be helpful to know that for the first 3.5 acts Homestuck was designed to resemble an adventure game, and the commands on the bottom of the page (linking to the next page) were submitted by readers, with the resulting panels being created in response to the commands. This leads to a fairly high level of silliness early on. Later it gets a bit more focused.