fix4j.org
fix4j.org is a collection of Java libraries and tools dealing with the Financial Information Exchange protocol (FIX), an "electronic communications protocol initiated in 1992 for international real-time exchange of information related to the securities transactions and markets" (source: wikipedia.org).

All our projects are available on github:

fix4j-assert

fix4j-assert is an open source library designed to assist in testing of applications using FIX protocol.

http://www.fix4jtest.org (homepage)
https://github.com/fix4j/fix4j-assert (github)

fix4j-fixpad

fix4j-fixpad is a simple GUI which allows you to view fix messages in a human readable format.

https://github.com/fix4j/fix4j-fixpad (github)

fix4j-test

NOTE: This project has moved to fix4j-assert.