I\'m not quite sure how to describe this in words without making it overly complex, so here is basically what I want to happen:
It sounds like you might be looking for cURL and cookiejar:
http://curl.haxx.se/libcurl/php/examples/cookiejar.html
This will allow you to programmatically login to a site, keep a session open, and then access the login protected content. Once you get the page contents, then you can use DomDocument (http://us2.php.net/manual/en/domdocument.loadhtml.php) to access the content you need and turn it into RSS data.
Edit: if the website uses form keys, like many do, this will require extra work to extract the form key from the login page and add it to the login POST