The title of this news item says it all. Click here
to go to Steam and purchase Titan Quest Gold for only $5. This contains the original Titan Quest
plus the expansion pack, Titan Quest: Immortal Throne
. I've been playing through the original (well, before Mass Effect 2 came out) and have enjoyed my experience so far. It's a no brainer click-fest with insane amounts of useless loot, but you'll get many hours of play time for your money.
Check out the demo and try before you buy if you are a little hesitant. The demo is a good indication of what you'll find in the full game. This discount ends tomorrow.