Of the many computerized star catalogs available, I really like the Guide series (as of April 1998 at version 6) from Bill Gray's Project Pluto. For asteroid and variable star enthusiasts (as well as many other astronomical interests) it is chock-full of useful catalogs and information. Bill Gray does a good job of keeping it up to date and is easy to deal with by email should the need arise. I especially like that it has the Hipparcos and Tycho data sets and Bill has added a feature to convert the Tycho photometric system to show Johnson V and B values for the Tycho stars (V mag and B-V value).
Bill also bundles with the Guide6 CDRom two very useful utilities for the asteroid hunter, Charon for astrometry and Find_Orb for quickly estimating orbits of new discoveries which can then be fed into Guide6 to make finder charts.