So I'm a little behind on this, but if you are anywhere near a Nike Store, you should stop by and pay a buck for a Live Strong yellow bracelet (chances are that you've seen people wearing them but didn't know what they were). The whole cost of the bracelet -- $1 -- gets donated to the Lance Armstrong Foundation in support for cancer research; in total, they are trying to raise $5 million. In addition to being for a great cause, your wearing of the bracelet shows your support for Lance Armstrong during the Tour De France race.
If you can't get by a Nike store, you can order a band online here.
As I pointed out to one of my single friends: if nothing else, the $1 bright yellow band is a very inexpensive conversation starter.