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.