Most researchers have encountered Technorati at some point -- it is one of the premier tools for searching blogs. What I have found particularly valuable about Technorati is how I can mine useful data about opinion-leaders in the blogosphere. There are two different search tools in Technorati; they both search blogs but they offer different features.

You can get to the Advanced Search page from the main Technorati page; just click the Advanced Search link. You have the usual options of searching for individual words, phrases, and words you do not want included in the search results. You can also limit your search to blogs about a specific topic, or even limit your search to a specific blog. This last feature comes in handy when I am trying to find a particular blogger's comments on a topic, as many blogs (including my own) do not offer a search feature. Interestingly, you can also look for any blog postings that include a link TO a specific blog -- this is useful for anyone who needs to monitor what has been blogged about a particular organization. You can also search by tag, if the blogger has assigned tags (a.k.a. descriptive keywords) to individual posts.

Technorati's other search feature is perhaps more intriguing for researchers; it lets you limit your search to blogs that have more "authority" than other blogs. What's authority?, you ask. It is a number assigned to every blog by Technorati, based on the number of other blogs that have included a pointer to that blog. Interestingly, Technorati only counts once for any blog's pointing to another blog; this addresses the problem of spam blogs that exist solely to boost the ranking of another blog by posting hundreds of links to that blog. So, for example, if I blog several times about LifeHacker, Technorati only counts that as one "vote" for LifeHacker's Authority ranking.

Technorati's Authority search page does not offer many search options; just type in the word(s) you want to search, and select the amount of Authority by which you want to limit your search -- any, a little, some or a lot. Note that you can also limit your search for blogs in one of 20 languages. (I wonder why this feature isn't over with the Advanced Search page.) Using the Authority search lets you see what the influential bloggers are saying about a topic, rather than retrieving blog postings in personal blogs. A nice feature is that you can click the Authority number in any search result and see what people have said when they pointed to that blogger. Are they agreeing with the blogger? Saying the person is an fool? Referring to the blogger as a respected expert in the field?

In fact, I have used these tools to identify bloggers who I want to follow for my own professional development or for a client. Say I needed to follow the key bloggers who focus on biofuels. A search for the word "biofuels" in all blog postings returns 32,000 blog posts -- a few too many for me to review easily. But when I limited my search to blog postings in English on biofuels by influential bloggers, I retrieved 7,000. Still a lot, but I can skim the first few pages of results and identify the 5 or 10 bloggers with high authority. And if I really want to narrow down the search, I can use the Advanced Search page to search for blogs on biodiversity and then, from search results page, further narrow the results to only those blogs with high authority. And finally, I could use the Advanced Search page to look for blogs that are ABOUT biodiversity -- a very narrow focus, but I know that all the blogs retrieved will be relevant.

One other finding tool for at least marginally more "serious" blogs is Technorati's Blog Directory. The blogs listed here have been "claimed" by their owners; that is, the blogger has used one of several ways to indicate to Technorati that she or he is in fact a person who is responsible for that blog, rather than a spam blog. This also has the effect of eliminating most personal blogs, as those bloggers are not particularly interested in raising their visibility. Unfortunately, the categories within the Blog Directory focus primarily on non-work topics such as Entertainment, Lifestyle, Politics and Sports, but it may be worth checking.