I just found this handy post that provides an easy way to debug your applications using the maven tomcat plugin. Using the tomcat plugin for maven makes it easy to test an application during development. In addition to that, this post provides a handy script to pass the java command line arguments needed to run your server in debug mode. Then is just a simple matter to connect it with eclipse.

http://blog.kadirpekel.com/2009/11/09/debugging-through-maven-tomcat-plu...