In response to this article from DevShed about creating a "simple and secure login script", Anthony Ferrara has written up this post to help dispel some of the inaccuracies, bad practices and security issues that could result from DevShed's code.
I decided to click the link [in my feed reader] and give the article a read. Not overly shocking was the fact that I didn't find the content of the article to be, how shall I say this..., overly factual. It's not really a "tutorial", but more of a "here's some code that's secure". A quick review of the code found more than one vulnerability, and some significant things that I would change about it (as well as a few "really bad practices").
He walks through each of the files included in the original tutorial - Authenticate.php, Register.php and Logout.php - and talks about things like brute force detection, password verification, registration handling and session serialization. He finishes it off with a list of twelve overall issues he noticed during his work along with solutions for each (usually very simple ones too).