Microlog is a small, yet powerful logging library for mobile devices based on the Log4j API. Supports Java ME (J2ME) and Android. Logs to device, to PC or to servers online. Used in all phases from development on emulator/device to outdoor field-testing.
The Winfessor Enhanced .NET Trace Library is written in VB.NET, supports class level configuration, and contains both console and Winforms trace receiver interfaces. To use it you simply put a Traceable attribute on your class and call a static method.