If you have data that kind-of lies on a line
but there are nasty outliers, try some variation on medians.
A good book is:
Rousseeuw, P.J. and Leroy, A.M. (1987), Robust Regression and
Outlier Detection, Wiley-Interscience, New York (Series in Applied
Probability and Statistics), 329 pages. ISBN 0-471-85233-3.