How long is the timer you use? Three minutes (std egg timer) or is it some lesser amount? (non-standard are far more difficult to find).
We actually have 1 minute, 1.5 minute, and 3 minute timers. (They actually can vary by about 15% on each use because they are cheap and plastic.) We use all three of them for different things.
For this skill challenge, I used the 1 minute timer, and it was the first time I ever used one that short. 1 minute is really not much time at all. As you may have seen in the broadcast, it came down to the last grain of sand a couple times.
For regular combat, we typically use the 90 second timer for each turn. We've never been strict about enforcing it, but I can say with confidence that just having that timer there as an encouragement to decide what you want to do really does speed up combat significantly. I've never once actually enforced the timer during combat, but when it gets low I'll point it out to the player and they'll usually just bite the bullet and do whatever they were thinking.
The 3 minute timer we haven't used in quite a while, but it was once used fairly often for encouraging role-playing. When we would get to a particularly interesting point in the session, like about to open the door to the Big Bad Guy's throne room, I'd put down the yellow 3-minute timer, point to one of the players, and say "what are you thinking?" The timer would be there to encourage people to take at least that long, rather than to speed them up. The idea was we wanted a few minutes from each player explaining what is going through their character's mind and such. It was a really useful little exercise but I am happy to say that the reason we no longer do that anymore is that all of the players now fairly frequently offer up that sort of information on their own, when relevant.
As for where I got them? My Friendly Local Game Store happens to carry them. I think they also have 30 second and 5 minute timers.