Tired of ASP.NET, which of the following should I learn and why?
I'll add in my vote for Groovy, as well as another one for Ruby.  Both Grails and Rails are excellent frameworks, although Rails will get you a job a lot sooner than Grails.  Both are truly a pleasure to work with, and have actually made me enjoy coding again.
Groovy is nice because you can use any Java library.  So, lightning-fast database access, XML parsing, PDF generation, and so on.  In a nutshell, Groovy is Java, if Java had been written by a bunch of Ruby guys.
Grails is also great, although it's a lot buggier than Rails, and if you want to do anything complicated you're going to need to learn a bit about Spring, Hibernate, and Java.   Grails does have better internationalization support and more deployment options, as well as a really good integrated scheduler (Quartz) for long-running and scheduled tasks.
Rails is Ruby all the way down, so you can very easily read the framework code and figure out how things worked -- I did this in order to figure out how to implement a graph (data structure), and was really pleased with how easy it was to figure out how to change things.
Which of the following technology is easy to learn and fun for developing a website? If you could only pick one which would it be and why

Clojure/Compojure+Ring/Moustache+Ring
Groovy/Grails 
Python/Django 
Ruby/Rails
Turbogear
Cappuccino or Sproutcore
Javascript/jQuery