At the risk of sounding like a shill...
You can't go wrong with any of the of the
Geneforge games, IMO. Not so hot in the sounds/graphics department (at least it keeps the system requirements low :p), but excellent story and gameplay. As far as gameplay goes, it's "real time exploration, turn-based combat" (though it still takes place on the same screen). While you only create the main character, you can summon up your own custom-made party of creatures to help you with the killing, or you can use fast talking and l33t machinery sk1llz to get you through sticky situations without getting your fancy robe dirty :p
Anyway, all of them are free to download and try out, you don't have to sign up or give out your email address or anything like that. They're all relatively self-contained, so you can more or less "jump right in" with the most recent one and not be TOTALLY lost (which isn't a bad idea, as the interface and technical aspects are so ridiculously improved over the previous games that it's not even funny, although if you have an older system you might not mind so much).
Anyway, that's my spiel, see you around.
EDIT: Oh yeah, personally, I liked the Baldur's Gate and Icewind Dale games better than Neverwinter Nights, if only cause you weren't constantly struggling with a camera that's always everywhere BUT where you want it to be, and uncontrollable party members that can be charitably described as "moronic."
Edited, Mar 11th 2009 9:34pm by RajiFarlander