Yes, Toledo is a wonderful place to visit if you are near Madrid. It's very medieval (there's even a museum of torture devices used during the Inquisition!), and if you know El Greco you can see the views of the town almost exactly as he painted them four hundred years ago or whenever. They also specialize in lovely gold-on-black artisanal stuff that I love. Also near Madrid (though I haven't been there) is the royal palace El Escorial
and also Franco's tomb
The above advice is great for Barcelona. Ooh! Also near Barcelona is Dali's museum and self-designed mausoleum
, which is totally awesome. And since it's a much bigger youth draw than Madrid there's lots of twentysomethings playing around Las Ramblas and that general area that has lots of hostels. I once joined in a pickup soccer game in a random plaza in the rain. But there's about a million interesting things to do and see in Barcelona.
I am going to Barcelona in early September. Too bad! International meetups are the best.