If you are interested in learning with others feel free to join us here.
http://thefx.org/brain/index.php?/topic/69-learning-houdini/
I have yet to find time to learn houdini but one day! I have shared some files for others to look. Of course you can upload your files to share as well.
You can download a free version of houdini here. You can play with all the features but you would get watermark in your renders.
http://www.sidefx.com/index.php?option=com_download
