Well, I've got the same problem...
I've got 2 propositions, though:
-LithUnwrap has a "optimize model" option which seems to work. For all my previous models, it removed only duplicated vertices, not polygons (but hey; perhaps my models couldn't be more optimized...

). Warning: Sometimes, this optimization moves the pivot to the center of the model. And I don't know if it works with animated models...
-Polychop is a wonderful plug-in for 3D studio max which decrease the polycount of your model according to the chosen percentage of detail you want to keep from the original model (I don't know if this is clear; my syntax is approximative...). Well, the plug-in is free, but 3DS max isn't exactly a freeware...
The links:
-LithUnwrap isn't supported anymore: the author made a commercial version of this unvaluable tool. You still can find the older (and free) version floating on the web, but it's not easy...
-Polychop can be found at the neverwinter vault, 'cos it has been developped by a Bioware's member (I'm not really sure of this.). Try this address: http://nwvault.ign.com/Files/other/data/1056040299413.shtml
I hope it helps, but I'd like to see more satisfying answers... Can someone help us ?
Ideas: memories of things which did not occur yet...