feed on feeds is a server side RSS aggregator with an interface that actually looks close to what my imaginary perfect feed reader looked like: single-page listing of all new items, sorted by date -- none of that three-pane crap. I've been using it for three days now, which is already longer than any other feed reader I've tried. :)
Plus, it's all PHP/MySQL so I shouldn't have much trouble making it look exactly like I want it to...