I'm currently reading The Power of Now by Eckhart Tolle which is a new agey, but interesting way of looking at the world.
For a more manly suggestion, I'd recommend the novel Love and Glory by Robert B. Parker which is not a self-help book but has a lot of great insight into how a man should live.
Also, Once an Eagle by Anton Myrer - required reading at West Point and another book that hides self-improvement in a great story.
I like 'The Way of the Superior Man' by David Deida. A little Woo-Wee but, all "self-help" books kind of do that.
'The Jerk that Women Love' or whatever the title of that book is by F.J. Shark. 'Double Your Dating' David DeAngelo. Those two aren't just about dating or just about women.
'Outliers' by Malcom Gladwell. Gives some interesting perspectives to how people/brands/fads become successful.
'Freakonomics' and 'Superfreakonomics' by the two Steves. Also gives interesting perspective of why/how things happen and that humans really don't make good or rational decisions. Usually it's a rationalized decision.