What I dig about Listia is that it's all free. The only thing I pay for is postage on the cards I sell, and thats pretty cheap. This has enabled me to pick up some cool stuff, like this cool stuff here.
2011 Diamond Sparkley Tyler Chatwood rookie card. 304 credits and I can check it off my want list.
1998 Pinnacle Mint Collection #22 Frank Thomas. I pick these up here and there. I think I have about half the set. 50 credits.
A couple of really nice 1965 Topps. Again, I pick up '65 and '56 Topps here and there, my two favorite designs. 754 credits.
And these awesome, I-didn't-even-know-they-existed 1971 Topps Football Game inserts. Scored two on two separate auctions netting me the Patriots team set. Jim Nance - 505 cradits, and Ron Berger only 106 credits.