Steam's third day of sales is
GO! Unfortunately, the site got smashed by traffic. I'll update as I get them.
As far as I can tell:
Left 4 Dead 75% off - £6.24
Trine 50% off - £8.49
Order of War 75% off - £7.49
Resident Evil 5 50% off - £14.99
Borderlands 33% off - £20.09
Ghostbusters 50% off - £7.49
Spore 50% off - £14.99
City of Heroes: Architect Edition 50% off (plus subscription) - £4.99
And that amazing THQ pack is still 50% off - only £26.49
Gog.com also have
30% off selected Interplay games. Some great ones in there.