There are some sites that are for teachers to get students. Try here for a few links: http://www.usingenglish.com/cgi-bin/...gi?query=skype
Other teachers have set up there own sites, try here for some links: http://www.usingenglish.com/links/Tutorials/index.html
I have no idea how successful they are in getting students. If it's not possible to get students through one of the sites in the first link, then it might be worth looking into advertising like Google ads or other similar systems or web advertising; I see a fair few such adverts around, so I assume there must be some return on them.