What the heck is that thing on top left?
That thing on top left?
The two Japanese characters shown in the logo are read as chishiki, they mean knowledge or information. I used this logo originally for my personal desktop wiki based on mediawiki, whose purpose is to keep my information (personal, professional, work, ... everything that can go into a computer) together. So, I thought chishiki is a nice word to describe its function. Then I started to like the logo, so started to use it here as well.
The two pairs of square brackets on either side is traditional to wikis, as it indicates the simple syntax for linking between articles in a wiki.
The English word seek does not relate directly to the Japanese word, but it represent another important aspect of wiki usage, to help seek knowlege.
See here for a larger version of the logo.