Athlon 900@1GHz (home) - about 3.4 WUs/day, depending on how much it's used, can very from 2-5
Athlon 1.33@1.5GHz (home) - about 6 WUs/day, steady, it never gets really hard use (gaming and the like that is)
PIII 550MHz (neighbours') - about 1 WU/day, it does 2/day when it's on all the time, but it's not on much
P4 1.3GHz (neighbours') - about .5 WUs/day, it can do 6/day when it's on, but it's almost never on
PIII 500MHz (best friend's) - about 2 WUs/day, it could do more, but it's under heavy load a lot
PIII 650MHz (friend's) - about 1 WU/day, it's not on all the time, and it's used to play games a lot
That comes out to about 13.9 WUs/day, but if I'm lucky and everything's on and not used too much, I can get about 20, but that rarely happens.