For the most part, I've just bookmarked feeds in Safari, and it's worked well enough. Whenever a feed updates, the number of new items appears as a number next to the feed name, so I can check feeds when they update, and only when they update.

Lately, however, I decided to take a stab at writing my own web-based reader. It's in the very early stages (hence the URL to it is obscured in the screenshot), but it's been fun to write. It makes very heavy use of Ajax.