Has there been an official release for the OST's for these games at all, and if so, where can I find them?

Half-Life 2 seems to have had a few promo CD releases, but that's about it.

I don't think there were any for the first game, but there are a couple for the second. These are the ones I'm aware of: The Soundtrack of Half-Life 2, Half-Life 2: Episode One Soundtrack and Half-Life 2: Episode Two Soundtrack.