Fotki. It's not free but it gives you more control to do anything you want than any other website. I've maintained my website on them since 2004 and will likely hit 500 thousand images next year...already there if you count my second account, the Cardboard History Gallery.
Basically, it comes down to you get what you pay for, and simply put, I choose to pay for the best.
VERY slow trading due to health problems. Not transferrable so safe to trade with, just moving is painful and can't always access the cards.
Cardboard History My COMC
New Collection Website: Cardboard History Gallery (Still under construction)
Tips on how to make your scans look like the card does in hand (No more washed out, fuzzy scans!):