A few of my friends have recently asked me how to share code between their applications. Here's a screencast walking you through how I solve this problem. It works really well for me. I hope this is useful to you.
You can get my terminal shortcuts from my dot files repo on GitHub. You can also find the test app and test library on GitHub.
The git submodule documentation might also be useful to you if you're new to working with submodules. If that's a little hard to understand (I know it is for me), just try googling it. There's a lot of good resources on submodules.