Here’s some I know of. As to whether they are the most appropriate tool for a given language, form your own opinion.
- .Net: NMaven and dotnet-maven-plugin
- AspectJ: aspectj-maven-plugin (still Java I know but worth mentioning)
- c/c++: native-maven-plugin compile with compilers such as gcc, msvc, etc …
- Google Web Toolkit gwt-maven-plugin
- PHP: Maven for PHP
- Ruby: Ruby on Maven
- Scala: maven-scala-plugin
- Flex and Air: Flexmojos
Arbitrary “integrations” can be handled by using the exec-maven-plugin to invoke the relevant compiler and binding the execution to the compile phase.
There are also Maven-like products such as Byldan for .Net
Updated with Flex Mojos and dotnet-maven-plugin at Pascal‘s suggestion.