I posted this recently on my blog but I thought I'd share it here:
You know the "Next Blog" link at the right of the top bar? Imagine if, using your Wordpres blog, you could set up categories whereby the "Next Blog" would take you to a blog in one of those categories, sorta like Stumbleupon.
The question is how do you define the categories? Well you could do it by using tag associations. So if you like music then it would take you to a blog that uses the category music. There may have to be a certain number of the corresponding tag for it to be classed as a category. For instance if a blog has one music post amongst thousands of others then it wont count.