This is a nice tutorial:
http://android-developers.blogspot.de/2009/05/painless-threading.html
Or this for the UI thread:
http://developer.android.com/guide/faq/commontasks.html#threading
Or here a very practical one:
http://www.androidacademy.com/1-tutorials/43-hands-on/115-threading-with-android-part1
and another one about procceses and threads
http://developer.android.com/guide/components/processes-and-threads.html