Articles, Blogs, Social Media Networking
There is one more word develop in recent years that is of Ariticles, Blogs and Social Network like Orkut, Youtube, Facebook and many more. More that 50% people visit these sites for search of knoledge and friends. So it is the second best place your advertisement on these site.
You can advertise by convensional ads, Ariticles related to your product or service, Blog about you product, research.
You can keep your customer updates through these Social Bookmarking and twitter without calling them to your website.