Using the 1.6 crop factor certainly works, but it might be interesting to work it out from first principles, too. The "normal" focal length is generally considered to be close to the diagonal of the image area (sensor, film, whatever). For 35mm film and "full frame" digital, this is about 43mm - 50mm is the closest common focal length for reasons that are interesting but probably not relevant here apart from indicating there's some range for variation.

So, another way to determine which lens is to find the dimensions of Canon's APS-C, and apply some Pythagoras:

sqrt( 22.2^2 + 14.8^2 ) = 26.68

So for a Canon APS-C, you might consider anything from 24mm* up to about 35mm as a good choice for a "normal" lens. If you wanted to get as close as possible to a 50mm, then the 30mm mentioned is likely a good choice, which we can see by comparing the ratio of 50mm to the theoretical 43mm:

50mm / 43mm = 1.16
35mm / 26.7 = 1.31
30mm / 26.7 = 1.12 – closest to 50mm
28mm / 26.7 = 1.04 – closest to theoretical normal
24mm / 26.7 = 0.89