http://fedora.redhat.com/download/mirrors.html the first 20-30 core mirrors
The only problem is to find the path, which to add into yum. It is described here
http://www.fedora.us/wiki/FedoraSources howto do that. But note, that every server has its own specialities, so the path might be a little different, so you have to play with the options.
If you want extra repros, then go to
http://www.fedoratracker.org and search for them.