Update (April 21, 2006):

If you're into the pay versions of VizUp, the new 2.14 version has been released. The freeware version (1.8) remains the same.

Originqal story (February 5, 2006):

After going pay-for-play for several years, the really wonderful model reducer and optimizer, VizUp, is back once again as freeware (1.8 version). The Pacoima Ranch development team did beta testing on one of the very early versions, and really likes this reducer. It works very similarly to some of the expensive reducers as it will progressively remove "extra" planes and polygons to reach targeted reduction levels.

The builtin OpenGL viewer allows you to actually view the models in various levels, so the end result is at least partially understood. It works best if used on small standalone models before  the model is placed into a larger world.