+1  A: 

Try the Sun Java petstore:

http://java.sun.com/developer/releases/petstore/

Or an older version:

http://java.sun.com/developer/releases/petstore/petstore1_3_1_02.html

Pablojim
+1  A: 

I would download Spring and check out some Spring examples too. Also take a look at this tutorial

Mike Pone
I actually already digged through some of the Spring MVC code, but is very difficult to reconstruct their logic without using Spring.
James McMahon
A: 

Maybe Struts 1 (with tiles) would be easier to grok than Spring, if you want to see how MVC works in a Java web application. Ignoring all the Struts tags, you end up with Actions (which are called by the Struts servlet), JSPs and a configuration file or two to tie them together. Lots of information online.

JeeBee
+2  A: 

I like Bear Bibeault's article from a few years ago. High level explanation, but very clear.

This is his implementation of an MVC "framework". I learned a lot by going through it:

Bear Bibeault's Frontman

Jibba