According to the sidebar on GameTap's Free Games page, it seems that MoonPod's Mr. Robot (no. 1 in GameTunnel's Top 100 Independent Games feature) will be added to the GameTap service as a free download in the near future (usually within one week).

The GameTap Free service requires no registration for free games which aren't rated mature. A 32 MB download is all that's needed to access free stuff like Sam and Max Season One: Episode 4, Blast Miner and Psychonauts.

MoonPod's Mr. Robot: Free on GameTap