Well, I don't think you will find such a thing in Madrid.
The only free wireless network in Madrid I know of is (
Madrid Wireless . However, this is a private network that lets you connect to the Madrid network. If you want to access the internet you would have to ask for permission to one of the owners of a node. Furthermore, there aren't many access points yet.
As for the libraries, a few of them has started offering free access but with their computers. They won't allow you to connect your laptop.
However, there is an Internet cafe, CyberFuture at Montera street that has 6 connections point where you can plug-in your laptop. It's more expensive than using the PCs, but perhaps it's more convenient if you want to download or upload something from your computer. I've tried myself and the connection was quite fast.
