The Internet Genealogy Service of the Church of Jesus Christ of Latter-Day Saints contains genealogical data of millions of individuals. This is a valuable resource, but be careful: the data is not always reliable, because many errors have happened while transcribing old records. But it is a good start, providing information about where to search and what to expect.
Don't miss stopping by the Bonitz surname forum at FamilyHistory.com. You probably will find the contact you have always been looking for!
Genealogy.com - Claims to be "The leading resource for family history". Is it?
The search pages at Rootsweb.com offer many different databases for a free search.
The genealogy software Brother's Keeper is a shareware program by John Steed. The appearance and performance of this software is excellent. Download your copy here!