I went from a Sole Prop to an S-Corp in January. The corp is taxed like a sole prop or partnership. There is no double taxation like a c-corp. No more self employment tax and I only pay income tax on what I and the IRS deem as a "reasonable salary". Every thing else is considered distributions to the share holders (ME). As an S-Corp, I don't have to have annual meetings nor have minutes of it. I am the Prez, Secretary and Treasurer and I made my wife VP.
It really depends on your type of business, its growth potential, the level of income it produces (tax rates differ from one form to the next) and how much paper work you want to keep track of. Definately talk to a good accountant and locate a corporate attorney in your area who can set you up. It costs around $500 for the lawyer, around $100 filing fee with the state and however much for the accountant.
Other advantages are being able to buy equipment with pre-tax dollars, and keeping your personal stuff seperate from the company.
There are plenty of books out there that explain the differences between the different forms of business as well as the pros and cons of each.