GRUMMP --- One free software which is used to generate the unstrutured, mixed-element meshes. you could visit the following website
http://tetra.mech.ubc.ca/GRUMMP/index.html
or just download it directly from :
ftp://tetra.mech.ubc.ca/pub/GRUMMP/GRUMMP.tar.gz
[推荐]Generation and Refinement of Unstructured, Mixed-Element Meshes in Parallel
I think Geompack++ by Barry Joe probably is more powerful...
You could get more information by search on google. The only
problem is that you could not get the source code and it only
works under Windows...