The tutorial on the android developer site is good. There are also a bunch of other good ones:
- http://marakana.com/forums/android/examples/48.html
- http://owenhuangtw.pixnet.net/blog/post/23760257-android-aidl-(android-interface-definition-language)
- http://www.app-solut.com/blog/2011/04/using-the-android-interface-definition-language-aidl-to-make-a-remote-procedure-call-rpc-in-android/
