Whether it's something from GOG.com or not, what are you guys currently playing, and what's the lineup for the next games you're going to play?
For me:
Currently: Fallout 2
Next: Freespace 1
Then: Baldur's Gate 1

I'm playing Fallout 2 as well...I'm not sure what to get next, though.

Currently playing Storm of Zehir (second NWN2 expansion). Next up is another run through Storm of Zehir, then likely I'll finish my Fallout 3 game. After that, I'm likely going to look at playing through Sacred Gold that I recently purchased from GoG.

I'm switching between games. I'm currently playing Half-Life 1, Sacrifice and Giants: Citizen Kabuto. Once I'm done with one of them (most likely Half-Life 1), I'll be buying something new from GOG. Or, more likely, I'll buy something new from GOG within the next few days, to take advantage of the 3 for 2 offer, but won't start playing any of them until then.

Disciples 2, Front Office Football 2007, Medieval Total War 2 (specifically the Broken Crescent mod) and Gal Civ 2.

Far Cry 2.

Right now I am playing Still Life, and I guess I will either start Far Cry 2 or FEAR when I finish that.

Fallout 3. Then Burrnout Paradise and my rapidly growing collection of GOG games. (Buy 2 get one 6 dollar game rocks. i already know what i'll get ;))

Now:
Fallout 3
Later:
Assassin's Creed
Left 4 Dead
Freespace
And I always find time to squeeze in some TF2.

Now:
Warhammer Online (most often, PC)
Morrowind (from time to time, PC)
Ultima: The Black Gate (sometimes before i go to sleep, PSP)
Later:
Fallout 3 (PC)
Red Alert 3 (PC)
Fable 2 (Xbox 360)
WoW: Wrath Of The Lich King (maybe, PC)

I am playing Disciples 2, Perimeter and Titan Quest now. I guess I'm going to finish Unreal 2, when I'll be in FPS mood again.
Oh, and I'm playing Warhammer 40k: Dark Crusade. But I play that pretty much all the time

randomly running those games:
Oblvion GOTY
Fallout 2
Disciples 2
Jagged alliance 2 (prefered last few days)
WoW (not so much last month)
L2 (not so much :) )
Mass Effect (for evil char now)
I have tried playing two games at once, but was reasonable only if one of them is turn based or doesnd need too much attention :P
Waiting games :
Fallout 3 with mods to play REAL fallout, not some kiddish pseudorpg.
Witcher Enchanted edition

Currently:
Tie Fighter (collector's ed.)
Witcher EE
Beyond Divinity
Coin Mcrae's 2005
Call of Duty UO
On Deck:
Fallout 1,2&3
BIA: Hell's Highway
NWN:SOZ

Right now Oblivion (Xbox 360), and Hinterland.
I would be playing Morrowind and VtM: Bloodlines, but I've hit some tech trouble with a load of my games at the same time.

I either play Dystopia (Cyberpunk FPS/Source Mod) - dystopia-game.com
or Fable at the moment.
I also have Diciples and Vampire: The Masquerade - Redemption started, and i wanted to play Fallout 3 a second time, with an evil char and lots of mods, to see the rest of the locations etc., but i just can't play a game again right after i finished it. Perhaps later.
I also should finish NWN (Blackguard Series, Fan Modul) and NWN 2...