The job of approving comments sometimes falls on a person who does/should not have access to the WordPress admin. By design WordPress only allows a user with admin privileges to do this job. I wrote an an External Web Interface for approving pending WordPress comments via XMLRPC.
Check it out, it is open source on google code:
code.google.com/p/wordpress-comments
Hello, I am Melvin Rivera; creator of 
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Nice looking app. We’ve got an email list for WordPress XML-RPC developers – http://lists.automattic.com/mailman/listinfo/wp-xmlrpc – that your welcome to join.
Great, I joined the email list and posted to it but still don’t see it in the list archives.
Great very great
Bah! That’s friggen awesome! I’m such a nerd.