This may sound stupid but it's the most important rule to join the list: you have to like Maria Gripe or her books in some way (why else would you want to join?).
You have to provide a valid working e-mail address (don't worry, e-mails displayed here are protected against junk mail) in order to let me get in touch with you.
You DON'T have to have a site. But if you have one and want it to be listed here, it would be nice of you to place a button or a text link to http://gripe.diletante.net somewhere in your site.
It doesn't matter what your site is about, but I won't list any sites I consider offensive for other visitors (don't worry, I'm very open-minded ;p).
If you have no site, you can put the link in your e-mail signatures or something like that if you want to.