The "Baby Bridges" post describes the game pretty well, but the "Math Time Fillers?" post isn't helpful at all. I thought I should change that.
The one math time filler I use frequently is Chocolate Math. The link explains the thing really well. I often use it in middle school classes when the students finish all their work quickly. I usually end up explaining it two or three times as the kiddos seem to enjoy it.
A really good site for various classroom activities is Substitutes, FTW! She has a whole category of math activities.
The other thing I notice in my stats? The post "Oops" continues to be really popular, especially with spammers. I have no idea why.
Have you tried Chocolate Math before? Know any other good math games?