Lots of stuff on sale, and it looks like each day will have some 24-hour BIG deals.
One of today's big deals is: Fallout, Fallout 2 , and Fallout Tactics
are all FREE
! - https://secure.gog.c...ay_winter_promo_2013
Note that there's a strong rumor that these titles will no longer be on sale on GOG after the new year due to changes in ownership of rights to the games. So get 'em while you can, and get 'em while they're free. (If you've purchased a title, the download remains in your account even after GOG no longer sells it - at least that's been true so far)
Understandably, the site is getting hammered.
It looks like the link to the free Fallout offers has been taken off of the GOG home page. It also looks like the direct link above still works. The site seems to be a bit better but is still pretty flaky, so I'm not sure how easy it'll be to get through the checkout process - or even if the offer might be cancelled (it looks like it was planned to be for today and tomorrow).