Try advertising in forums that could have a potential audience by buying Ads space from the forum owners. If your budget permits you can also advertise about your services in your local town/city in the newspaper or magazines. You can even sponsor events, etc.
I'm also looking for a good place where to start advertising our vmware VPS server rental services.
Our prices, here, an online calculator: serveru-noma.lv/en/server-rental/server-rental-prices
There are multiple ways of advertising. You can do
Running a PPC program
Classified sites is good way to free advertise for your hosting services