Fallout 1+2
Die by the Sword + Expansion
Kingpin: Life of Crime
MDK 1+2
M.A.X. 1+2
Messiah
Freespace 2
Redneck Rampage Collection
Sacrifice
Giants: Citizen Kabuto
Thank lawdy lawd everything here is < $10 so I still have money left for women and beer. Problem is I now only have time for GOG and beer. Ah well...can't really complain.

So far, their entire library consists of games I *haven't* played before! This is great, but it also means I have to think long and hard about which games to buy. At these prices, my main limiting factor is time. If I had limitless time, I'd buy, buy, buy.
So, I have to have priorities. I've bought:
1) Fallout (game finished)
2) Fallout 2 (game in progress)
3) Descent1&2 (game in progress)
4) Freespace 2 (not yet installed)
based on recommendations, my next purchase will *probably* be Giants. Who knows what'll happen after that? Depends on the library; but I'm in a very action or RPG mood lately.
Cheers!

Descent 1 and 2
Freespace 2
and just bought Fallout
Love this concept and will support this service any way I can.

I got giants and shogo. Waiting for the earthworm jim games. I might get sacrifice, MDK1+2 freespace 2and soldiers .
edit: got freespace+expansion

I purchased Conquest of the New World and picked up Fallout 2 as the free pick from the Interplay promotion. I own most of the games listed, thanks to the Interplay 15th Anniversary Anthology, but I couldn't get Conquest to work for nothing. I think I've put around 20 hours into it the past two or so days.
Fallout 2 comes after Fallout. I still have a few hours left in it. And that is after The Witcher. But I'm getting to it, and it'll be nice to have those set up for the third.
I think Descent 3 is next. I remember hearing nothing but good things about it when it was released.

I've bought Kingpin, Shattered Steel, Perimeter, Shogo, Redneck Rampage Collection, Fallout, Stonekeep, Earthworm Jim 3D, and the M.A.X. Collection so far. Out of the games I don't have I already owned most of them: Descent 1-3, Freespace 1&2, Fallout 2 & Tactics, Giants, Hostile Waters, Jagged Alliance 2, MDK 1&2, Messiah, Original War, and Sacrifice.

Right now I have Fallout 1 + 2 (btw: I've heard some funny theory that gog.com is actually part of Fallout 3 promo/advertisment funded by Bethesda :-D ), MDK 1 and Sacrifice. And many games on my wish-to-buy list :)

Just Kingpin ATM, but I'll be buying a lot more when I finish upgrading this PC.

I bought: Descent 1&2 package; Fallout 1, Citizen Kabuto, Jagged Alliance 2.
I will definitely buy: Fallout 2, Descent Freespace.
I will probably buy: Descent 3(don't remember this one, maybe I will when I play it), MDK.
I might buy: Shattered Steel, MDK 2 if I like the first one
Games of the above that I've bought in the past and am buying again now either because I lost the discs or want the programming GOG put into them to make playing and installing on Vista a snap, or just to support the GOG concept:
Fallout 1 and 2, Descent 1 and 2, Freespace

Bought FallOut, Fallout 2
Planing to Buy: Freespace, Freespace 2, GIANTS: CITIZEN KABUTO

I bought Fallout 1 and got Fallout 2 as my freebie.
I plan on buying Freespace + Expansion, Freespace 2, and Fallout Tactics.
I'm thinking about Colin McRae Rally 2005, Shogo, Giants, and Descent 3.

Just Fallout 1 so far.
Plan to purchase:
Fallout 2
Fallout Tactics
Freespace 1
Freespace 2
Maybe Redneck Rampage. Boy, would that bring back some memories...

Too much already ;)
-Descent I & II
-Descent III
-Freespace I
-Freespace II
-1nsane
-Redneck Rampage Collection
-Toca Race Driver 3
I'm planning to buy Operation Flashpoint as well. I already own the original, but the game + expansions drm-free for 10 bucks, that's a steal! (just as everything else...)

'till now I've bought:
Fallout 1 & 2
Decent 1 & 2
and
Decent Freespace 1
Finishing them before buying new ones.

Fallout, Fallout 2, Descent 1 & 2, Descent 3 + Expansion, Lionheart: Legacy of the Crusader