Xtrade is a project mainly written in Scala, it's free.
Simple comparison trading project example in Scala
Simple trading example project to compare with ztrade, the Java counterpart.
Uses Scala 2.8.1 Specs2 JUnit Mockito SLF4S SLF4j Logback SBT
Acceptance testing using Specs2
Highly recommended to build Intellij IDEA and/or SBT