I get this sometimes since updating to iOS 6. Here's what works for me, I can generally go to each app in question and tap it (like I'm trying to launch the app), wait a few seconds and the update seems to always proceed after that. It's like it needs an individual kick-start to get it going. I then wait for it to finish, and repeat the same procedure for each app waiting to update.
Give it a try, it works for me...
Sent from my  iPad 3