I concluded that one of the best sort of games to get for a netbook are ones that are DRM-free since DRM solutions usually involve (a) a disc being in the drive (netbooks not having a disc drive by default) or (b) being connected online all the time (which is fine if you've got an Internet connection all the time, but occasionally getting an Internet connection may not be possible or too expensive).
So I started looking for distributors who sell DRM-free games. Fortunately I already know of two:
1) Positech Games. I bought a game or two from this developer (he's known as "Cliffski") and he firmly believes in DRM-free games which is a plus.
2) Good Old Games. Another bonus with these guys is that they sell some classic games!
I've heard that Stardock sold Galactic Civilizations and the sequel without DRM but recently it's introduced a DRM scheme, although I'm not sure if this applies to all their games now. Might be worth checking out though as I thoroughly enjoyed the Galactic Civilizations series.
Direct2Drive might be worth a look too. I bought Puzzle Kingdoms off them and that was DRM-free too, although it may be the fact that Infinite Interactive don't put DRM on their PC games rather than anything that Direct2Drive aspires to...