As with all marketing you have to remember it is not sales. Marketing is about connecting people to people (that includes within your organisation) as well as connecting them to products, services and ideas. Once you know who you are connecting (target market) and to what (products or services) then you will know where to advertise or promote your product. You have to realise this fundamental revelation about the world: everyone you want to reach is already out there, already connected and you just need to find where they are and help them connect not only to you but to those around them. (See my blog on tribes).
This is a fact: 90% of all consumption of media (including all time spent on TV, radio, and all websites including internet banking and email) is spend on social-networking sites (such as facebook) for those aged 30 and under. (Source BRW Magazine)
That is amazing! SO when you consider where to market, where your customers are, consider social networking sites. And its cheap!