Hi - I'm a bit of a pregnancy app junkie at the moment :) I have baby centre's and the march of dimes cinemama apps too - they are great! I also have one by Pampers called Hello Baby that shows week by week real pictures of what your baby looks like. At different milestones you can even get a 360 degree view, and it explains what is developing on your baby each week. I had it on my iPad for my last pregnancy and this time it's on my iPhone as well. It's pretty cool.
A note about the Cinemama one - it asks you to login with Facebook. That really freaked me out as the last thing I want is some app posting information about my pregnancy to Facebook - especially since I haven't told many people yet. I looked into the settings a bunch and I was able to "not allow" the app to post on my behalf at all, and I also changed the settings to private so that no one can see anything about the pregnance (just in case!). So you may want to just be careful when you're setting that one up.
Congratulations and have fun!