Probably best know is Seth Godin. Seth has so many thought provoking one liners that leave you questioning why you do what you do. Well known for a number of books such as The Purple Cow, All Marketers are Liars, Permission Marketing and now Linchpin. I recently had the opportunity to listen to him speak at an "Art of Marketing" event in Toronto and he captured an audience of 1,600 on leadership and how art is replacing the machine.
Mitch Joel, author of Six Pixels of Separation, provides some interesting illustrations of game changers that are reshaping our way of doing commerce.
These game changes are around us today so no need to look to the future. He has an interesting story about Journey (yes the 80's rock band) using YouTube to find their latest lead singer.
Mitch, who is Canadian, was referred to as the "Rock Star of Digital Marketing" by Marketing Magazine and definitely worthwhile to follow his blog or on Twitter.
Thirdly is T.S. Kelly, who I have heard being referred to as 'the professor', provides an interesting read on his blog The Media Strategist. With over 20 years in the media research industry in places such as Nielsen, Quantcast, Havas Digital and his own consulting practice, T.S. provides everyone with an in-depth perspective on todays digital marketing ecosystem. Definitely a big proponent for hybrid methodologies and I definitely recommend a read of this posts Hybrid is the new BLACK and his view on Preserving Local Radio's Relevance.
Our landscape is changing at a pace never experienced before. I'm sure these three will remain at the forefront of helping us all navigate through it.