In my post MicroISVs, I mentioned this valuable market research tool for researching a software product category, called Data Sources. It lists information about all the products (names, features, and pricing) available in a software/hardware category as well as a lot of valuable information about each software/hardware manufacturer such as employees, sales, history, and products.
A number of posters have been inquiring about it. It is not available at Amazon, but you will probably be able to find it at a sufficiently large or sufficiently technical library. It's a thick reference in small type, numbering thousands of pages and published in three volumes twice a year. It is also a subscription costing about $500 a year from Ziff-Davis Publishing Company, 20 Brace Road, Cherry Hill, NJ 08034, (609) 354-5000.
Update: A quick search on the Internet generated the following information about the book. "Data Sources: Software. New York: Ziff-Davis (semi-annual) Ref. HD 9696 .C3 P3." I was unable to find the ISBN#.