Remote Login via Finder: Choose user account without entering password
I accomplish this in Safari:

vnc://username:password@server


If I then create a bookmark, whenever I execute it, it will open up without prompting me for the password. For the sake of convenience, I save the bookmark to the desktop.

EDIT: Additionally, you can copy the bookmark to a location (such as the desktop), and change the file extension to .vncloc to open Screen Sharing directly.