I've read so many books I can give you a list of suggestions however I'll narrow it down to my top two:
Gravatational Marketing by Jimmy Vee, Travis Miller, and Joel Bauer: Though it's not specific to real estate it's an excellent book on marketing for any business. I highly reccomend it.
Endless Referrals by Bob Berg: Again not real estate specific but gives some great information on networking to get business. Especially with other agents.
As far as the furture of real estate marketing The Swanepoel Trends Report has one out for the future of real estate marketing 2008. It looks really good and I plan on getting it. Lots of great info on technology and social media which is where the industry is going.
For sales, I have always been a fan of Brian Tracey and The Sandler Sales System.
Hope this helps!