I have prepared a list of Java-based MVC frameworks; click on details for any framework that piques your interest.
Please let me know about other frameworks that should be listed, or about broken links (many of the older small frameworks are gone from the web). If you sign up (not ready yet), you can add new ones yourself; they are "moderated" until I verify them, to avoid spam.
Who's Using Web Java?
There is also a list of major/high-volume web sites based on Java to answer the question "who uses Enterprise sites based on Java Web Tier?".
I have also built a number of implementations of a simple web form using some of these frameworks. The goal of these implementations is to capture the results of a typical "signup" web form, validate it, and store the results in a database.
The implementations are the following. The source for these is on my GitHub account, in the jwf-impls repo.
I wanted to learn how these various frameworks compared. :-) And, the Frameworks catalog was prepared in partial fulfilment of the requirements of the Master of Science Degree at Staffordshire University. Here is the original academic report from 2004