One of the nice features of Firefox 2.0 is that you can assign other applications to be your feed handler (when you click the feed icon in the address bar) including web-based ones like Google Reader or Bloglines. I personally use a local install of Gregarius. The latest version out of SVN has a button to register your install as a handler, but in case your wondering there are a few ways to add a custom handler (from the Gregarius forums):
Secondly you can create some preferences (strings) in the about:config area where # is a number that is not already being used by Firefox and the URI part is the subscribe url for your web application (%s is where the feed URL will go):
I had to restart Firefox to get it to show up in the preferences. The third way is even more involved and requires editing the user.js file in your profile directory. You would add the following lines:
Again thanks to the people in the Gregarius forums for pointing this out.