For me it is social media which includes bookmark sharing and blogging.
I run and manage quiet a few blogs in the area of my products and services. After a calculated planning and posting now I get daily more than 30 visits in each blog. 30% of those visits gets converted as visitors to my main product web site. But this things takes time and planning but they leave ever lasting effects compared to ad sense. Trust me its a full time effort one has to put.
Adwards has done a good job initially but than suddenly I found everyone else in the market is also competing for those well researched keywords and I was not able to compete them.
You have to again create a very strong buddy net in various community and social sites. For me they work like just mouth publicity.
One interesting fact : I am using DigsBy and normally I have around about 200 people connected with me using gTalk,Yahoo and Hotmail networks. i effectively use Status lines of DigsBy to promote everything.
it would be very interesting to see what others have to say about it.