I picked up a 64 MB Max Memory PS2 memory card for $4. It was opened but the card seems to work just fine.
I also picked up Computer Gaming World's 200th Issue CD (March 2001), which has a bunch of demos but also includes several full DOS games that I'm not entirely sure are completely legal. It has Achelon, Alpha Man, Avoid the Noid (!), B-17, Balance of Power, Betrayal at Krondor, Bunniflip, Elite, Elite Plus, Empire, Kampfgruppe, Mystery House, Net Hack, Pirates 2, Reach For The Stars, Rogue, Super Dune 2, Tac Ops (Taco Ops? No? Dammit), The City, X-Com, and Zelda Classic. That was... $5. That's way more than I wanted to pay for it.