Unfortunately, it is never that easy to find a local willing to take the time to walk some foreigner around their home town and show them the sites. The exception, of course, is hiring a private guide. Those tend to be expensive, however.
Last summer, City Sherpa in Helsinki, Finland, combined the best of both worlds and provided a service where local experts could show tourists around free of charge. Finnish volunteers posted short bios about themselves online and a brief description of their area of specialty, ranging from music, to art, to history, and more. Visitors merely had to email the guide they found most interesting and if they weren’t busy, a tour would be arranged.
There doesn’t appear to be any news on if the service will continue this upcoming summer, but the bios are still online and so are the email contacts. So, if you happen to be setting off to Helsinki, shoot one of them an email and see if they are still performing this great service.