There are a number of free links databases where you can post your site. Ours is here: ESL Web Directory
You can find some others here: Web Guides - ESL Web Directory - UsingEnglish.com
There's not much in the way of free advertising- most sites go for paid banners or text adverts.
You should be able to use free software like Skype, a whiteboard that will cover most needs without buying anything.
- For Teachers