I have recently added Ruby on Rails to my repertoire and as I start a
new project, I find myself wondering: Why are so many of the postings
I find as I search for help from 2006-2009?
Should I start my new project with RoR, ASP.NET, Python/Django, Zen?
Is RoR thriving or dying?
None of those frameworks you've listed are in any danger of disappearing
in the foreseeable future. I would no make my decision based on this
Ruby on Rails is most definitely in very active development, and there's
no sign of that stopping. Rails 3.0 is currently in it's third beta and
is now in the home stretch of a final release.
If you read any of the blogs on Rails 3 you'll see just how devoted the
core team is to making this an outstanding release of Rails.
As for the other frameworks you mentioned, I have little advice to give.
I've not really used any of them so have no option on them. As for me
ASP.NET is not even a consideration as it's a Windows only platform.
Python/Django is interesting, but the little I saw of Python I think
I'll stick to Ruby. Zen I'm not exactly familiar with unless you meant
PHP and the Zend framework.
At the end of the day all of these are still very viable options. If you
like Ruby on Rails there is no logical reason not to choose it that I
can see. It certainly continues to be my choice.