As an alternative to advertising if you want to appear on other websites you could submit interesting editorial for them to include on their site with a link back to your own site.

This will give you more coverage than a standard link and help to raise your credibility in your chosen field.

When Zarr hosts your website you can see exactly where visitors are coming from so you can see if you have submitted articles which are the most popular, and whether they have had any impact..

Alternatively if you have a product website you could offer them a copy to review and include on your website or even as a competition give away.

These are methods of promoting your website which involve time and creativity rather than money.