Managing so many Trading Cards

How do you guys manage so many trading cards ?

Any app, website, tool that you use? please share.

I have hundreds of cards(i know many of you have thousands) from so many games, plus I will have a lot more by the time sale is over.. How do I even begin organizing .I need to know what to trade, what to craft and what to sell :s

Any pointers/suggestions would be much helpful.