You'll want to check out the FMS forums on Eric Brouwer's R/C Homepage:

http://www.n.ethz.ch/student/mmoeller/fms/forum/

He and other posters offer dozens of links to great (and not so great) additional models you can download and install into FMS.

Most of the new models are saved as .zip files. You'll want to extract them to your C:\Program Files\FMS\Models\ folder.

Some of my favorite downloads came from:

http://kimagure-hikoki.hp.infoseek.c...er6/index.html

This link has 8 or so pages full of various models for download.

Good luck and good flying!