The only Blizzard game that has a chance of showing up on GOG is the original DOS Warcraft, since that is the only Blizzard that is out of print.
Another vote for No One Lives Forever..a really good game that never got the sucess it deserved.
Would not mind seeing Civil War Generals from Sierra either.

You forgot the first Diablo (at least individually). I've been looking for it for ages (have lost my copy).

It's not like you see WarCraft II BNE in stores nowawdays either, not even their own store has it.
<edit>Also BlackThorne and Lost Vikings</edit>

Rock and Roll Racing, too.

Diablo and Warcraft 2 are pretty easy to find to buy on the Internet, though. Just google.

It's not like Monkey Island, Psychonauts, Baldur's Gate or Fallout is any harder to find online, but nonetheless they're all either already on gog.com or VERY high on the most wanted list...

Don't be so sure. THQ got Homeworld rights, true (source), but only the IP, not the rights to publish previous games. What I mean is that THQ is entitled to make Homeworld 3 if they want, but Homeworld 1, Cataclysm and Homeworld 2 are still Activision property.
An other evidence: Metaboli says Homeworld 2 publisher is Activision.

If that's not simply out of date then Activision must somehow have retained publishing rights, like Interplay did with the earlier Fallout games. Simply retaining the rights to the old games isn't enough. They'd have to have permission to use the IP too. Which is out of character for 'let's drop anything we can't make over 9000 sequels to' Activision.
Furthermore, I wouldn't use a site that boasts about having '247 players online' as an up to date source of information. There's no way they could afford to keep it up to date and it's probably forgotten about by both publishers anyway.
Still. It's possible they still have the right to publish those games. But why haven't they appeared on GOG? It doesn't make sense, no matter which way you look at it.

Is Homeworld compatible with Windows XP/Vista/7? Anybody?
Because if not, perhaps it's not easy to make it compatible.

Probably they'll try to get the remaining Activision titles released as soon as possible, probably one release per week as they have now, to allow Activision properly evaluate the profits from using the service. Weren't they supposed to make another announcement this month?

I think all of them are compatible with XP and Vista at least, but I'm not entirely sure. Haven't tried them in Windows 7 yet, but I might find the time to do so this weekend.

oh hell yes, No One Lives Forever 1 and 2. Both unplayable on modern systems. Would love to replay those puppies.

Isn't the Activision month over already?
I am not a big fan of their games. The only one I enjoyed and found ground breaking awesome was "Turok" (with it's sequels), but that was on the N64 and irrelevant.
How about the old South Park game? Full pissed snowballs ftw.

Sure, but that doesn't mean that no more of their games will be added to the catalogue.