Grails (http://grails.org) is probably the most interesting new web development environment today. It is built on top of the following:
Spring
Groovy
Sitemesh
Hibernate
Quartz
It's also extensible with plugins
http://grails.org/Plugins
You can watch a few of the screencasts to get an idea of the functionality.
http://grails.org/Grails+Screencasts
The one very appealing thing to me was that Grails can easily be integrated into an existing Java/JSP project. There's no need to rewrite the project from scratch.
I think Ruby on Rails would be a great option if you didn't have any legacy code or if Java wasn't your day job.
Finally, I like the idea of being able to deploy Grails projects to application servers such as Tomcat, WebSphere, Glassfish, etc. These systems are extremely reliable and they scale well.
