One of my most earliest memories is of an Apollo mission launch, which my family was nearby for, visiting relatives in Florida when Jeff and I were kids. It was the first nighttime manned launch, and it was past our bedtime, but we were at the side of the road so we could watch as the night sky lit up as if it were mid afternoon.
One of my strongest memories, years later, is being in the VIP stands for the launch of Columbia. It wasn't its final flight, but after the loss of that shuttle, the souvenir mug I picked up at KSC became that much more important. The memory of the launch never fails to get me choked up. You can feel the vibration of the engines, at your core, before you can hear them. This was a daytime launch, but was still visibly quite bright. The sound itself was never overpowering, but the rumble grew and grew.
I don't expect to make it to another spacecraft launch anytime soon, but I do watch every launch I possibly can live on TV.
The countdown is about to resume with nine minutes remaining. You can watch on NASA TV, on HDNET, on CNN, or at http://www.nasa.gov/ntv (I have the NASA iPad app running with HD video, a little over two minutes behind, as well as CNN on the TV for roughly live coverage.)