checkout this article on CNN.com http://cnn.looksmart.com/og/pr=FastSitesCustom;tc=;pc=15;ro=1;rc=222;pi=zch|http://cnn.com/2002/TECH/space/11/19/blackhole.merger.ap/index.html
although the two black holes wont actually collide for a couple hundred million years, I thought it was interesting how the gravitational shock from the collision will change the distance from one point to another sligtly in the universe

-GreaterEvil

they would probbly pass right through eachother, same as when galaxies collide.

Actually, they will collapse into each other due to their insane density. Theres a ton of info on this subject at www.nasa.gov if you are interested.

-GreaterEvil

They would have to be on a very close course to not get sucked into each other's orbit (or pass by with altered direction.)

Still, theoretically if they pass by close enough then they will merge into a single, more massive, black hole. The same thing can happen with stars.

They will be a massive black hole but only for a while.