Email alerts on SharePoint document libraries and lists can be based on a view but RSS feeds are for everything in the list. If you want a filtered RSS feed then you can use the Content Query web part (this one is for the person using a Spot watch to get SharePoint tasks).

As an example, my resources list on wssdemo.com has over 1,000 items but if I wanted to create a feed of just the public web sites hosted on MOSS from this list I would add the content query web part to any web part page, specify the filter condition and enable the RSS feed

Here is the feed generated by the web part...

http://www.wssdemo.com/_layouts/feed.aspx?xsl=1&web=%2F&page=7cbd50bc-aa88-457c-bc2e-33703120a8b2&wp=d7acf8e9-5950-49c4-a060-5cca1d0c2d2c