Well, there is, quiet a few of them. The best free one I found for XP is yod'm. There is the free version which goes up to version 1.4 and a commercial version (I think it is at http://www.deskspace.com/ ) if you want to pay a little and help the developer out.
You can find links to both plus more information here-
Also, if you like Aero 3D on Vista, why not run it on XP? You can by going here.
I ran both in tandem today and they work fine. Yod'm doesn't quite have all the cool features that Beryl has, but I hear there is a Beryl port for windows coming. Yod'm or the commercial version with more features should hold you till then.