The homepage has the top categories (those with most followers) and lists the top five tweeters/twitterers (not sure what the term would be!) in each category. You can click on the topics on the right hand side of the homepage to find people in different categories, and you can use the search box to find categories which aren’t featured on the front page. You can see a list of librarians currently on WeFollow which ranks them according to the number of followers they have; I’m currently #12.
To add yourself to the directory, just send a Tweet to @wefollow and include up to three areas you would like to be added to. For example, I sent the following message:
@followme #librarian #web2 #university
That’s the basics, although Phil explains WeFollow in more detail in his blog post so rather than repeat it, here’s the link to his post.