err try this :
http://web.cecs.pdx.edu/~gerry/nmm/c...rtSolution.pdf
they discuss a few methods for solving the eqn. also the version of the colebrook eqn. that Usama217 asked about seems wrong I'd use the one they discussed above if i was you, that is
1/sqrt(f) = -2 * log10((e/3.7D) + ((2.51/Re*sqrt(f))))
seems correct plus i've seen this in two text books adn another lecturers notes so i'd believe this to be more correct it's possible the one Usama217 quotes is a manipulated version of the one i quote above but i can't see how :)