It would be handy for me if the site included the dimensional analysis of units; I was converting Kilowatts to hp, and noticed that a watt was '1 Joule per second'. Outstanding, but what the heck is a Joule? I went to it's conversion page... and saw it converted to watt seconds. This wasn't as helpful as I would have liked.
Meters per second probably doesn't need a dimensional analysis published; it is obviously m / s; no problem there... but it would be nice to know exactly how more complex (or at least just SI) units break down into fundamental units. 1 Watt = 1 kg m^2 / s^3 and 1 Joule = 1 kg m^2 / s^2 is sometimes exactly the info needed; please consider adding this.