If you've got skills to share or are looking for someone generous with their expertise, TeachMate provides "a dating service in education." Enter in what you'd like to learn and find someone who can help, or offer lessons in a subject you know well. You can set a location to find teachers and students near you, and if none are found, subscribe to email notifications when a match comes up. A quick scan shows many current users are in Europe, especially Russia — which makes me think it might also be a great way to meet locals when traveling and participate in some cross-cultural exchange. TeachMate is a free, open-source online application.
TeachMate

</img> </img> </img> </img>