TF2 (And friends) General chat
TF2 Website- Updates and News from the TF2 Team.
TF2 Wiki - Everything you need to know about TF2 in one place.
Meet the Stats - Various statistics on items, their qualities and other interesting information.
TF2 Raffle House - Free raffle site.
TF2B - Faster backpack browsing.
TF2 Items - Comes with loadout info, item and backpack history.
OPTF2 - One of the fancier backpack viewers, shows almost anything you'd want to know.
TF2 Outpost - Trading site.
TF2TP - Another trading site
TF2 Bazaar - Yet, another trading site.
TF2WH - You can trade stuff for credits and trade credits for stuff.
TF2LS - Lists all the items you have, you haven't and in which quality you can find it.
TF2 Toolbox - Some tools for managing your backpack.
TF2 Tags - Post your ideas for named items, descriptions, or paints on hats or weapons.
TF2 Gallery - See screenshots from TF2 of hats with different paints and effects.