There are some really great Open-Source products available - and Blender is one of the best.
I was lucky enough to meet Ton Roosendaal and many of the Blender team recently. I was inspired.
It's an excellent tool for exploring visual elements - lighting, composition, camera angle, depth
of field, bokeh, highlights, shadows, narrative, and so on and so on. You can also create, mix,
and composite video as well as stills. In short, a really nice end-to-end solution (which integrates
with external renderers such as V-Ray and other products - such as After Effects) that allows
me to leverage what I know about the GIMP into some other computer-based stuff.
There are plenty of free tutorials and training available, I will posts renders I am proud of here.
You may also see some animations that I have made here: http://vimeo.com/user6097634
You can download Blender for free here: http://www.blender.org/download/get-blender/
While I have not been completely happy with publications from Packt (http://www.packtpub.com/)
they do at least provide high-quality books about Blender, GIMP, and other open-source
products - with some of the profits going back to fund the products themselves.
Disclaimer: Sorry if this sound off-topic or like spamming - I have no financial connections
to either the Blender Foundation or Packt Publishing. Except that I have purchased materials
from both of them.
[Update: Cool! It turns out 23HQ even has a group for Blender. I have just joined it.]