Edit: check the second post for current info. Initial post left as is for posterity. Also, finally fixed the typo in the title!
Based on some experimentation, I've created some ball-park estimates of touchdown speed vs the mass fraction of parachutes equipped on a given lander. (using version 0.20)
-redacted-I say "ball-park" since these experiments were all at Kerbin sea level, and extrapolated via the barometric pressure of the other planets given in the wiki, and does not factor in the differences in gravity. All test flights were taken to a 100km apoapsis (+/- 1km) and uncontrolled until touchdown. Not shown is the difference between standard and drogue 'chutes (though it is comparable to the difference between the Kerbin and Duna curves). Please point out any errors that you find. (kerbin data sample)