Toothfairy is a Java midlet for chatting on mobile devices via a Bluetooth connection. It creates a network of devices using a simple but powerful ad-hoc routing algorithm.
LibDreamSpeak is an example implementation of the TeamSpeak2 protocol (client-side) in Java. Some day it may be used as base for alternative TeamSpeak2 (mobile?) clients.
MGnutella is a J2ME implementation of gnutella v0.6 p2p network protocol. It is in alpha stage now, which is not stable,not well tested and fragile. We are planning to develop both for devices supporting MIDP 2.1 and Android OS.