APRSdroid is an Android application for Amateur Radio operators. It allows reporting your position to the APRS-IS network and displays nearby stations as a list or on a map.
APRSdroid is Open Source Software written in Scala and licensed under the GPLv2.
If you really like APRSdroid, you can support the author by buying the Market version. You will get automatic updates and a good feeling.
You can also get the sources and follow the compilation instructions.
It is also possible to download the APK for manual installation.