There must be more, but this should at least give an idea:
These sites certainly didn't need me to advertise them, but hey, perhaps by concentrating them on my page I've made myself into a mega-portal! Send your friends to this page!
There are, by the way, other possibilities. Numerous sites concentrate as many good links as they can find about a particular topic. Once you find a site like this on a topic that interests you you're best bet is to bookmark it and use it as your homebase for future searching on that topic. Two wonderful sites that offer hordes of information and aren't owned by mega-companies are: