Over the last few years, data-packed CD-ROMs have hit the genealogy market at a brisk pace. For $20 or $30 a pop, you can buy CDs containing marriage and census indexes, compiled genealogies, military and land records or pioneer biographies.

With luck — and a couple of hundred bucks — you'll find an ancestor or two, or a clue to an earlier generation. But most genealogists can't afford to buy every CD that sounds promising. Fortunately, you have an alternative.