re: I was at home, watching it live on the NASA feed...
I found out about Columbia and 9/11 in the same way: for both events I'd just awakened, and was mor or less out of bed but had not yet activated any news sources. In the Columbia case, I even had a thought, "hey, shuttle lands soon, better go turn on the TV".
Both times, I got a phone call from my best friend at MIT. "Dude, someone just flew a plane into the World Trade Center, looks big". "Dude, the shuttle broke up on re-entry over Texas".
Next time I get a call from him before 9am, I'm not sure whether I'll answer.