Atangeo Balancer is a popular tool to optimize and simplify 3D models.
Its exceptional performance and a novel user interface allow finding
perfect balance between visual appearance and the number of polygons,
quickly and easily. Balancer utilizes a high quality polygon reduction
(aka mesh simplification or decimation) to preserve the visual
appearance of your model. The model features, normals, texture
coordinates, layer boundaries are all honored by Balancer.
Balancer also features fast and effective triangle reordering to
speed up rendering by optimal utilization of GPU vertex cache.

Check it out, all your feedback is highly appreciated.
Hope you will find Balancer useful.

Atangeo Balancer technology is also available as an SDK,
which is 32bit and 64bit binary libraries for both Windows and Mac OS X.

Link: http://www.atangeo.com/