Anyway, just for clarity, a further example. If you’re using permalinks, you can use this format:
http://domain.tld/category/categoryname/feed/

On my site, that translates to:
http://gobecky.net/category/ask-the-gimp/feed/

There’s a fab article at Perishable Press that goes into this in much more detail:
http://perishablepress.com/press/2008/03/09/what-is-my-wordpress-feed-url/#4

Oh, and to link to the feeds in my sidebar, I used this code:
queried_object_id;
? >
< a href=”"> RSS Feed
? >