Inkworks, the company that brought us great trading cards for Buffy, Angel, Firefly and Serenity, went under last March, a victim of the lessening economy. Which is a damn shame. They made some great products, and president Allan Caplan really enjoyed his work.
If you’re still looking for those last few cards to fill in your collection, apparently their remaining stock was purchased by Factory Entertainment, a company that has been selling cards through eBay for a few years now. They’ve created a site to list their inventory at inkworksarchive.com, but everything there (plus lots more) gets sold through their eBay store. No Firefly cards, not a lot of Serenity, but plenty of others from their biggest franchises.
For a look back, check out my interview with Inkworks’ Allan Caplan from 2006.
http://www.poplollies.com/trading-cards.html still has Firefly cards and Serenity cards.