Oh I don't know if I can name the exact five most recent. Let me kind of lump a few together:
Nostalgia purchases: a bunch of old modules such as Forgotten Temple of Tharizdun, Expedition to the Barrier Peaks, Against the Giants (compilation), Bone Hill, and a couple in the Slaver's Series. My brain gets a huge thrill from reading through these old modules -- it's almost literally a trip back to my childhood. It's not that I have the itch to run them, but the nostalgia factor is a fun part of the hobby.
Goodman Games modules: I'm not sure what it is, but I've been snarfing these up as I see them. I do want to run these. I'm not sure I'll ever have the chance.
Advanced Bestiary: Has some cool templates.
Arcana Evolved - Transcendence. I wasn't going to buy this, I already have "too much" stuff and I know my players won't buy, but I thought what the heck, I might be able to mine it for ideas down the road.
Akashic Nodes for AE -- haven't given it a thorough read, will be able to mine for ideas.