Can't say exactly but I can tell you mine roughly.
glxgears really isn't a very good testing platform as I'm sure you realize, its only an indication of whether 3d acceleration is occuring in opengl.
P4 2.0a Ghz 512k cache 512mb pc800 RDRAM with GeForce ti4400 on kernel 2.6.0-test5 and driver 4496 on RedHat 9.0
glxgears with default window size runs:
15212 frames in 5.0 seconds = 3042.400 FPS
18832 frames in 5.0 seconds = 3766.400 FPS
18842 frames in 5.0 seconds = 3768.400 FPS
17834 frames in 5.0 seconds = 3566.800 FPS
17390 frames in 5.0 seconds = 3478.000 FPS
That is also with numerous processes running and servers alive (although most are sleeping) so it would vary widely for a real test.
I remember testing that on a PIII 600mhz GeForce I and it was roughly around 350 fps but this was RedHat 7.0 and very poorly configured so that isn't much help either.