Cait and I had an enjoyable evening with Bookworm Adventures. Penny Arcade’s endorsement and related comic sum up our reactions pretty well (from Tycho’s point of view, of course). Top words so far have been “malevolent,” “whitehead,” and “battening.” The Mastermind-like minigame is great fun on its own; I hope I can find it or some variant separately, because you can only play it once per life in story mode.
PopCap doesn’t have a Mac version, but Bookworm Adventures runs just fine under Parallels (sans hardware acceleration), especially with the Coherence mode from the latest beta.