I was wondering how I can get Broken steel, The Pit and all of those add-ons for the PC version of Fallout 3 without having to buy the game of the year addition. Anyone have any ideas? If this is the wrong place to post this I apologize.

All except Mothership Zeta can be purchased on disc wherever video games are sold, so like Wal-Mart, Best Buy, Gamestop, etc. Mothership Zeta can only be purchased through Games for Windows LIVE. All the others can be purchased through LIVE as well, but it's the only way to get Zeta.

as Deadlykris mentioned, you can download them via GFWL. however if you look for a sale you can get the GOTY disc version for cheaper than what you'd pay for the DLCs individually. i got lucky and snagged the goty edition for $25 at amazon. the DLCs alone were ~$10 each (technically 800 points or whatever it was) when i got it (not sure how much they are now).

also, Mothership Zeta is included with the GOTY version.

Yeah, I should have clarified about MZ - Live is the only way to get it individually, but you can still get it bundled with the GOTY edition.