Tired of ASP.NET, which of the following should I learn and why?
You should wait until you get an answer from someone who's used more than one of those.  That said (I've only used rails, python, and javascript), one way to frame it would be as a balance between sheer intellectual joy and practicality.  My thoughts on Rails and Python from that perspective:

Rails is going to be different and interesting, and it was hip in 2005-2007.  There may be something more hip now.  (Hip counts when you want to get future colleagues excited about what you've done, when they haven't done it.)  I'd venture that it's at least as eye-opening as something based on LISP or Smalltalk or Haskell, but probably more practical because you may actually end up using it at a job or for contract work.  Clojure, Seaside, and HAppS sound really cool, but until one of them really catches on, you're unlikely to ever use any of that stuff again in your career unless you're a computer science PhD working with other PhD's.  (Edit in response to comments: please don't read this as a disparagement of those frameworks.  As Rayne and MarkusQ have noted, depending on your motivations, they may be just what you're looking for.  I'm just trying to communicate one method for weighing the alternatives based on your goals.)
Python is a great language to know all around.  I haven't used Django, but it has some industry traction (not as much as rails).  Python as a language though will serve you well no matter what you do -- it's great for banging out utility scripts and rapidly prototyping ideas.  There's a huge community and tons of libraries.

You can gauge a technology's potential usefulness for moneymaking by searching for it on craigslist, dice.com, monster.com, etc.
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