I chose the Colorado 529 plan because it's deductible on Colorado state taxes and they have an option that's run by Vanguard that allows you a decent amount of control of your investments. I did a little bit of research into other states, I didn't see any that were much better without deep digging.
We're putting less than a quarter of our "college" savings for our kids in there, in case they decide not to go to college, but I figured some tax breaks are better than none.