For STS 3.0, the way that template projects are accessed has been changed, so it doesn't surprise me that you don't see the template project in the dashboard. However, you should see it in the new dialog. I'm not sure what could be happening. You could have a look at your error log and look for relevant stack traces (and paste them here).
Or you could install STS 3.1 or later. The easiest is probably to just go to the git repo where the template project exists, clone it and import it into your workspace as a maven project.
Here's the repo:
https://github.com/SpringSource/spring-mvc-showcase
The only difference between doing that and using a true template project is that the template project configures a few things automatically for you, like the base package and the project name. All this can be changed after importing, however.