best 3 i have found for comprehensiveness. NewIsFree includes many different ways to insert news feeds on your site, from js to includes to java etc... It is extremely customizable.
The other good thing about the first 2 is that they include many obscure and specialist feeds as well, so your site can look very different from the ubqiuitous moreover news feed. Check the updating behaviour as suggested above, but its well worth the extra trouble to get a more targeted and specialised feed.
Geekboys specialises in tech/webmaster/unix/php related feeds.