Here's what I play on my mid-range laptop:
Civilization 3, SimCity 3000, Sid Meier's Sim Golf, The Sims (forget the add-ons, though, they'll slow down the game too much for a 4MB vid card), Total Annihilation (a classic!), Half-Life (in 640x480 mode), and Tropico.
Star Trek: Bridge Commander demo kinda works, but I wouldn't want to try the full version on it.