From WordPress 3.4 onwards, we can log into WP backend using custom URLs such as yourdomain.com/login or /dashboard. For those who do not wish to wait that long, here is the quick tip on how to do it now without a plugin. Please note that rewrite isn’t a good place to implement it. That’s why it is
going to be implemented as part of the canonical API in 3.4.
Here is the rewrite that should do the trick for /login, /logon, /login/, logon/. You are welcome to play with this rewrite rule for maximum fun!
RewriteRule ^log(i|o)n\/?$ http://yourdomain.com/wp-login.php [NC,L]
Please change the name of yourdomain in the above code.
Happy Rewriting! :)