You can use a htaccess file to rename the login and registration addresses to easier to remember versions:
http://wpguy.com/articles/an-easy-to-remember-login-address/
Using what was in that link we can further extend the simple login address into a simple signup and a simple register address as follows:
RewriteRule ^login$ /wp-login.php [L]
RewriteRule ^signup$ /wp-signup.php [L]
RewriteRule ^register$ /wp-register.php [L]
Remember these need to go directly after the RewriteBase / statement