Here's some interesting Info for Half-Life 2 posted over at Half-Life 2 Fallout! and don't forget to check out Mr Chimp's six-page write-up on Half-Life 2's Source engine! Great article well worth the read.

Half-Life 2 is about 3.5 GB uncompressed and about 2 GB compressed. This doesn't include CS:Source, HL-1:Source, DoD:Source, the SDK, or whatever. It's just the straight HL-2 sizes.

Half-Life 2 Info

Source: Belly of the Beast by Mr Chimp