I think that any article or blog that you read will always say that there are some free options for marketing online (besides social media.) Do you believe this, and if so what free marketing do you suggest.
I always fear the tag 'free' because most times, you don't get value for the money. When it comes to marketing, I prefer to spend some money. Social media is the only medium that I'd say is free to some extent.
If you use Project Wonderful, if you have credits in your account you can place up to 200 free short-term ads on sites that don't have other ads. If someone bids on those sites your ad will be removed for a paying customer. Their network focuses on comics though, so from experience I can say it works better for sites selling something geeky.