IK has a free version of SampleTank 2, and its a fully working version
of SampleTank . It is able to play a range of free sounds that they
publish on their site.

If you have not tried this, this program is awesome. The sounds that
they give are great as well.
It can be downloaded at http://sampletank.com/Main.html?STFreeDwn

They are also offering a free download of a new program similar to
SampleTank called Sonik Synth 2. This program is awesome, especially
if you are into vintage synths. It also comes with a selection of
sounds.
Download at:
http://soniksynth.com/Main.html?SSFreeDwn