Here's the trial for simmechanics for 30 days:
http://www.mathworks.com/products/simmechanics/tryit.html
Here is the list of blocks used in simmechanics (full documentation of blocks used in Simmechanics of simulink):
http://www.mathworks.de/products/simmechanics/blocklist.html
And here some demos:
SimMechanics Link is available for download at:
http://www.mathworks.com/products/simmechanics/description4.html
HTH,
Arnaud