I'm ADHD too, actually, and my biggest problem is being paralyzed by worrying about which task to choose. Once I get past the first five minutes of HEY HEY GO LOOK IN THE FRIDGE AND HEY CHECK EMAIL ONE MORE TIME, it's pretty easy to get in the zone. If I sit down and just do something, I'll probably waste an hour or two here and there on fun-but-unimportant projects, but it at least keeps the wheel greased. There's a momentum that builds up.