In the wake of the ridiculously awesome Portal-related ARG going on, Valve recently distributed images to a variety of games web sites. No web site has received every image, but they’ve all collectively put their images together:
While I’m not expecting them to provide some cross-platform thing to make PC games play on the mac, I do hope they somehow let me have the Mac version of the PC games I bought through them (like the ones listed in the post above).
Unfortunately that’s probably highly unlikely just because a lot of them were ported by a third party (Aspyr does a lot of it, I think), and they’re going to want their cut.