When in London, visit the British Library in Kings Cross. Free wi-fi, desks with built in sockets, pretty inspiring environs. There are a limited number of seats though, so get there early!

This is a fantastic room. It's hard not to be creative there.

Since I rarely travel with electronics, I use the New York Public Library for internet access when I'm there. All you have to do is get a library card. Not sure why I'd need wifi.