Deckbox is a website that helps you organize your trading cards, create decks and trade with other people. The supported games are Magic the Gathering, World of Warcraft and Warhammer: Invasion.
When signing up you will be asked what games you play. For each selected game, there will be 3 sets automatically created for you:
Creating your collection
Now head over to the Import section of your inventory. If you have already entered your card collection on a different site, forum or in a spreadsheet document, you can paste them in the textarea here to add them all at once, and you're done! Else, you can use the autocompleted input to add the cards one by one (people that have a really large number of cards sometimes choose to only add rares and some uncommons).
Having your cards in the Inventory, now you can browse through them, sort and filter them by different criteria and add the ones you want to give away to your Tradelist.
There's an Import section for your Wishlist as well, so if you have posted your wishlist on forums, or sent it to friends before, just paste it in there, and you're good to go!