Is there an Arachnologist in the house?

So about four days ago I was sitting at my desk (yes, this very desk) when my lower right leg started itching a lot. I am terrible at leaving itchy spots well enough alone, so I scratched at it, then discovering that I had four nickel-sized lumps on my leg. They looked and felt like big spider bites. Now, four days later, the lumps have been replaced by angry red circles, and a blister has formed in the middle of each bite. To see a picture, go visit the wife's blog about this subject. If you know anything about spider bites, or know somebody who knows something about spider bites, I would like some free consultation on what might have bitten me. That is all.