I've featured this site a couple of times on the blog here. Mainly because I know how much overlap there is between card collectors and comic book collectors. You can be one without the other and visa verse or just collect comic cards or non sports cards, but I know there are quite a few of you out there that collect both like myself. I'll be honest my comic reading preferences have changed a lot since I started collecting comics in the mid 80's and I don't always have the time to read everything I want to or for that matter the funds to buy all I want to.
But if your a comic collector you should really check this site out.
Back when I first found this site it was called My Comic Pile, but soon after I started using it, the makers upgraded the site and truly made it a comic book realm.
The best part about the site is you can make a profile and enter all your comics into it and see how many you have, what you have, what they're worth, even use there great reports function to see holes in your collection, which comics are moving in price, what your most valuable comics are.
They also have ton's of news, links to comic blogs, previews and new release lists, and you can buy and sell on their forums, plus they also list links to eBay for selling stuff. The site is free, donations are graciously accepted. By far the best comic collection site I've seen anywhere. Pretty much a one stop shop for the comic book collector.
Check it out.