The following websites are great places to trade/sell/talk and make your collection much better very soon after you join!!! I am registered on all these sites. Please join them and have some fun!
http://s10.invisionfree.com/hoopstradingandtalk/index.php (My forum! Best place on the net to trade and talk sports! Please join! Need Mods all the time since just started. Contests posted one right after another. Great traders too! Can buy cards with points just by posting! Have our own Fantasy NBA League!)
http://www.elitesports.proboards31.com/ (list nbaballa4life as your referer)
http://www.sportscards.info/community/index.php?s=d3a715556856443e963a48094ed4c9f8 (list nbaballa4life as your referer)
http://hobbyinsider.net/forum/index.php?s=afb29c6edebe73ca73b4b3ee45f8546b (list nbaballa4life as your referer and/or reference)
and some good buying sites:
http://www.naxcom.com/ (very cheap prices for very good cards)