Other thought: You could put a specific list of the type of work you do on the back, so as to keep the front clean and uncluttered.

My thought is this: ideally we hand out these cards to people that we've had plenty of time to interact with, and they should see the card and associate it with our face. In reality, though, especially at conferences and conventions, we end up leaving them on the table or quickly handing them to people are trying to move on and see everything there. Therefore, the card needs to represent *YOU* and all your skills adequately so that folks can look at it and have a bit of recall about what it is that you can provide.

That's just my $0.05. Take it or leave it as you wish. :)