What's the best programming language for a hobbyist?

That really depends on what's exactly your "Hobby". I'm a hobbyist myself, but I'd like to study Computer Science (I actually like the SCIENCE in computing.) and become a Software Developer.

But I'm not in College yet, so I'm a "hobbyist", people are suggesting Python: I'd say it's a great language, specially as first language or language for scripting... but you should try other ones too.

Given that you are a hobbyist you want to have fun, learn new things: Try Prolog, Scheme, Haskell, whatever.

I'm not a big fan of Ruby myself: Python does better in the desktop and I like Django (Python web framework) more than Rails. Although Ruby is nice as language too.

The language which moves my brain the most is Lisp. It's built around pointers and memory locations but garbage collection, cons, and car take away the tedium I associate with C. The REPL provides the instant gratification of instantaneous frustration while pondering the possibilities of macros offers a mental infinite loop.

But what is really great about Lisp when it comes down to it is the literary tradition. I just haven't seen another language which comes close. There isn't a Richard Gabriel for Fortran.

Python

I'm going to swim against the tide here and suggest that you might want to go back and play with Pascal some more. Pascal was the third programming language I learned (after machine language and Algol) and after all these years (including decades of working professionally with C, C++ and Ada) Pascal is still the language I have the fondest memories of. I loved it because it was simple and elegant and I could get my mind all the way around it (something I was never able to do with Ada).

There are still implementations of Pascal available, including Free Pascal and GNU Pascal. For more information about implementations, check out the Wikipedia article on "Pascal programming language".

Alternatively, if you want to get a solid foundation in Computer Science and algorithms, I would suggest you work your way through "Structure and Interpretation of Computer Programs" (abbreviated SICP). This was the textbook used for years at MIT for their introductory computer programming course, and the course materials are still freely available as part of MIT's Open Courseware program. I personally prefer the original version that used the Scheme programming language, but you could also go with the updated version that covers the same material using Python.

Edit: There are easier courses out there, but I think this one is the best if your are serious about getting a solid foundation in Computer Science.

Depends on what the project is. If I'm building a web app, then Ruby or Python. A mobile app is Java (android). A local script that does not need to be blazing fast or light is done with Python. If I need to deal with a lot of text then Perl. And I just want to get something done and have fun with it then Common Lisp.