I have Contact Form 7 set up on one of my websites ( http://pdirail.com/contact-us/ ) running WordPress 2.9.1 and it works perfectly with a Selectable Recipient list dropdown.
I installed it on my new site ( http://iesllc.info/contact-us/ ) running WordPress 3.0.1 with identical setting, form, tags, and list. The recipient list does not show up.
I can send a message to the default recipient with an attachment, so I know that part is right. Am I doing something wrong, or is there a problem in 3.0.1?