There are many sites such as daypop.com and blogdex.com that can tell you what subjects are hot in the blogging world. And that's invaluable information if you've just released a new product and want to see what the world—or at least the part of the world that is online—is saying about it.
What we particularly like about BlogPulse, which is produced by Intelliseek, is its ability to graphically pinpoint blog news to specific time periods. So let's say Apple wants to look at blog mentions of its recently released Tiger operating system. Steve Jobs would enter those terms into the BlogPulse search bar. When the results are displayed, he would click the "Trend this Search" icon at the top of the list. This produces a chart that shows blog activity by date. You can click on the peaks to see what the buzz was that day. In this case, the big news was around the April 29 launch date, but you can also see more blog mentions generated on June 6, when the Apple-Intel relationship was announced.
This information will not only give you links to specific content about your product generated around the Web, but also provide a view into what specifically generates interest in your product or company.