There are several of different seminars/classes that can help with this, and not just in a superficial way -- they really help you not only be more secure with yourself, but also figure out what you really want out of life and how to get it. I have heard good things about The Road Adventure (mentioned previously), but I also know people who have benefited from The Landmark Forum, Millennium3, and other places. They're all getting at the same thing, just in different ways -- they're about finding joy, peace, and acceptance in your life. The one that rocked my world was Pathways (www.gopathways.org). It really did change my life, in a GREAT way. Check 'em all out and see which one sounds like it might resonate with you.
As far as books are concerned, here are a few I liked:
There is Nothing Wrong With You: Going Beyond Self-Hate (A Compassionate Process for Learning to Accept Yourself Exactly As You Are) -- Cheri Huber
Loving What Is *and* I Need Your Love-Is That True? -- Byron Katie
The Power of Now -- Eckhart Tolle
Ending the Struggle Against Yourself -- Stan Taubman
Excuse Me, Your Life is Waiting -- L. Grabhorn (GREAT book! And you can get a workbook, too, to help put it into practice)
I hope you find the one you love! Good luck!!!!