Forrester Research: Technology research and advice.

Forrester Research is geared towards the IT Professional, as well as Marketing and Strategy Executives, and has both free research and timely reports on specific areas for a small fee.

Though it is slanted decidedly towards corporations rather than the entrepreneur, Forrester has quite a bit of information that is useful for someone starting a product online, as well as the many ways in which it can be marketed. Some of the first reports on the business blogging trend came from Forrester.

As the site states, you can gain "strategic insights on today's biggest market challenges, best practices, and trends."