I've been asked to do a little tutorial on installing a ClusterMap on a blog. Well, the good news is...it is simple to install. The bad news...there is a pause in new registrations until the first part of September 2006.
To install after they start accepting new registrations, click on the above ClusterMap URL, click on 'Get One'. It has been awhile since I did it, but I think I went through a registration process (my username, password, blog address...the normal information), then I was given a code to put in my template.