I got the game at the beginning of last week.
Had a ball with the campaigns, they got a lot of flak but I liked them quite a lot. Had some fun getting creamed by Brutal AI for a while, and then thought to myself, "Hey, I thought the whole tech tree was supposed to be available in Skirmish - where's the carpet bombs?"
The goal!
This led me to deezire.net, the only Generals modding website I currently know of. I remembered that Deezire had made a great mod for RA2, and went on the forums to see what I could find out.
After trying out tons of crappy programs to open the BIG's, I finally found
http://xccu.sourceforge.net/, and the XCC Mixer within was reliable and easy to use - more than I could say for some of the others I tried.
The bringer of the Carpet Bomb.
So, now that I could open up BIG's, it was time to get busy. After downloading XCC Mixer, the first thing I did was extract the Generals soundtrack from music.big and burn it
Why wasn't this in skirmish?! 
Then I started looking around some of the files that the sticky threads from the top talked about - Science.ini, SpecialPowers, FactionUnit, etc. Although there were a few tantalizing entries such as "POWTruck" and "Tomahawk waypointing," most of it was greek to me.
RTFM? WFM?
More later![/b]