BlogWatcher is a Japanese blog search and analysis tool. It comes from an academic research group and is, therefore, less constrained by traditional consumer facing UI issues. The result is an interface that throws up lots of interesting data:
The top graph shows message volume as a histogram and burst as a red line. The bottom graph shows counts of postive and negative messages including the topic searched for. The graphics are interactive. Note that the data spans 6 years of data. You can drill down into the graph and get more constrained views of any window.
Search results also provide details of positive and negative language within actual posts as well as classifying blogs and online diaries (which have traditionally been a separate class of content in Japan - predating blogs).