Wizards of the Coast declared that all D20 products must be sold through to retailers by the end of 2008 and the rest destroyed. You may remember this familiar tactic from White Wolf, and hopefully WOTC will note what happened to them afterwards.
The result? Goodman Games put all their D20 products at 50% off on their website (we followed suit in the store). This actually means we're selling their product at a loss, since our costs are 50%, but there's another 4% or so associated with incidental costs (credit card fees, bags, office supplies, etc.). Other D2o companies, most of them long done with their product lines, are actually thinking their best solution is the recycling dumpster.
Honestly though, at this stage of D20, I might take new product if it was given to me, but this stuff is a big risk even at 90% off. A year ago I would be making phone calls to snap it up. Now I'm just glad it's not on my shelves. Well, not a lot of it anyways. We've got about half our Ding & Dent bookshelves crammed with D20. At it's height you could value that shelf at around $25,000. We bought it for about ten cents on the dollar (so $2,500). Now it's worth maybe a penny on the dollar ($250). The effort to wheel it to the dumpster seems not worth it.
So what has value in D20? The Wizards of the Coast D&D books, technically D20, are immune from this purge, I'm guessing. However, they've declared they'll be out of product around this time, and D&D 3.5 books are already hard to find. Distributors are wiping them from their systems the moments they sell through. Nevertheless, we're still re-ordering popular D&D 3.5 books from WOTC, seeking them out where we can find them. Also considered still of value are Paizo adventures, both stand-alone adventures and the Pathfinder series. As much as I've railed about the company in the past, Paizo makes the best adventures, although some people still like the slog of a Dungeon Crawl Classic (yawn) or the official mediocrity of a WOTC 3.5 adventure (the 4.0 ones are much better).