Georg Lukas

APRSdroid - APRS Client

Paid

Comprehensive APRS Client for Android Devices

yaxim - XMPP/Jabber client

Free

yaxim (Yet Another XMPP Instant Messenger) is an XMPP client with a clean user interface and open source (GPLv2).

Bruno the Jabber Bear (XMPP)

Free

Bruno is the cutest Jabber/XMPP Instant Messaging (IM) app available. It is a themed version of the open source yaxim app.