Dk
SGMy backpack.tf review by Dk4Q This is one of the best sites. Made by the owners of tradeit.gg, scrap.tf and marketplace.tf which are extremely trusted. I use this site mainly to check the value of items. There is obviously more things to do than just check the value of items. You can trade items for keys or keys for items and so on.
Cookievoylol
USReally good if you want to trade on tf2 Really good if you want to trade on Tf2, the classified listings allow you to list and look for very specific items and there is a value on almost every item because of a very active price suggestion community.
Mihail
BGBest Tf2 Trading Site Out There! Best Tf2 trading site ever and forever! The only problem with it is that sometimes the prices aren't right which is normal, after all they can't update them 24/7 and it's up to the community which makes it amazing!
Emre
TRGreat TF2 site Great TF2 site to look for what you want.