Integrating M2Eclipse with an existing Maven project

If you're importing an existing Maven project into Eclipse, you have to so some manual configuration to get both of them happy.  The problem is that Eclipse constructs a webapp directory structure a certain way while Maven has slightly different expectations.  You need to modify you classpath and build directives manually.

This was extremely helpful: 

http://www.devx.com/java/Article/36785/1763/page/2

It was especially relevant in the section toward the bottom called "Some Manual Tweaking of WTP Internals".