2) Think about reducing the number of links on the homepage, and increasing the amount of content. Maybe a greeting for new users letting them know what your about. Overall your homepage is covered in links and as a user at first glance nothing stands out and I'm likely to hit the backspace button.
3) Create a better site structure (clear tiers of content), its very hard to navigate your site.
4) Get rid of empty pages like this: http://www.cardboardconnection.com/2011-topps-tier-one-baseb....
5) Make sure you aren't copying other's content and they aren't scrapping yours see: http://www.copyscape.com/?q=http%3A%2F%2Fwww.cardboardconnec...
6) Save posts like these for Twitter and Facebook: http://www.cardboardconnection.com/hockey/amazing-patches-fr...
7) A new design with larger font, different colour scheme and better plugins (commenting, ratings, etc) is in order.
8) Get rid of the Hot Auctions tab, link to eBay from the product page and not a secondary link farm looking tab.
9) Despite all these minor problems (and there's more) the quality of content on site is pretty poor, I guess if I was coming for the history of some cards maybe your site would be helpful but the content is written in a detached, impersonal tone that doesn't garner links or Google rankings.
Focus on writing high quality articles based on your/author's personal experience and expertise.
Check out www.copyblogger.com for more information on how to write well for the net.
10) Try and get in touch with Matt Cutts (http://news.ycombinator.com/user?id=Matt_Cutts), he regularly helps out sites that feel like they have been harshly treated (proof: http://www.seroundtable.com/google-ban-cutts-support-14164.h...)
11) After you have fixed all these problems submit a reconsideration request to Google.