In your own space, post a rec for fannish and/or creative resources and spaces. Tell us where you go to dig up canon facts for your fandom, or where you get all the juicy details about your favorite ship. Where do you like to hang out and squee like a squeeing thing?
For canon facts, wikis are always good. For Star Trek, Memory Alpha (film & TV canon) and Memory Beta (book canon) are great. Through Memory Beta I now know how Crusher and Picard came to be married (still can't quite get my head round it though). The Doctor Who Legacy wiki is the best source of information about the game.
Most other fandoms-specific wikis tend to be a rehash of Wikipedia and don't tell you a great deal.
For hanging out, it's all LJ and DW. Twitter is for real life, Facebook similarly, given it's names, not pseudonyms. I'm not into looking at pictures (except of bunnies), so I don't have a Tumblr.
Going through my bookmarks for other resources, which got a bit long...
When it comes to other resources, John Roger's blog is really good for Leverage and The Librarians. He explains all sorts of things that you don't notice. Reading it, I understand more of what goes into those series.
The Avengers Forever is the episode guide I use to work out if I've seen an episode or not. Although it invariably ends with me realising I have five minutes in and re-watching it anyway. Which is how I have still not seen all the Emma Peel episodes, despite having owned the box set for several years.
The Doctor Who reference guide is really useful because it lists all the episodes and audios and stories and comics. Some include more information than others about what happened in said episode/audio/story/comic, but at least if someone mentions a title you can look it up here and know which Doctor it is and what media and where it fits into canon.
A Teaspoon and an Open Mind for Doctor Who fanfic. Not easy to use for commenting or uploading fics, but if I want to read some Doctor Who fic, this is the first place I come.
Stories of Arda I don't visit as much these days, but it's great for LOTR fic (and a design that I find really easy to read).
Written? Kitten! is a great writing incentive tool - for every 100 words you get a kitten (and you change the number of words and the incentive).
List of Random Names is helpful for coming up with names.