http://www.clickandinc.com/llc_vs_s_corp.asp
http://www.taxguru.org/corps/scorp.htm
With a LLC, you will pay self employment taxes on everything. With an S-corp you only pay self employment tax on a "reasonable salary".
With the S-corp, and with the LLC, you pay taxes on your 1040, so you will still have the potential for AMT, etc, and you will be means tested on certain deductions. But if you have a "loss", you can pass the loss onto your personal income, thereby reducing it.
With a C-corp, you cannot pass losses, but your "salary" is whatever you say it is. You would then pay self employment tax on this and report it on your 1040. Anything else you pass is considered a Dividend and taxed at the divident rate. Anything not passed it kept as an asset in the corporation. You also can deduct something that cannot be deducted with an S or LLC.