I'm assuming you don't skateboard, when you're framing shots you really need to show the entire obstacle so you can see exactly where they're going/coming from to really understand what's going on. In most of these you just completely missed the obstacle and it just doesn't really work.
Your title caught my eye; my daughter is into skateboarding, and I've been hesitant on how to take 'action' shots such as these. I love what you did here, agree with the comment above. When it comes to movement, whether it's humans or animals, the photo looks best when the viewer can see left to right as to what is taking place, in order to 'convey' that movement. I do like these though. #6 down from the top, is my favorite.
This forum is funny when it comes to skateboarding shots... I posted some a while back and got slated because I showed the obstacle and where the skater was coming from and going... Everyone thought they should have been shot like you have done, in the air with no sense of what theyre actually doing. I recommend looking at this guys shots to see how to take proper skate shots http://www.thephotoforum.com/forum/photojournalism-sports-gallery/331614-skateboard-shots.html