I am currently working on a member's area for my website.
If you are comfortable with PHP and MSQL then it is not difficult to achieve.
There is an excellent website click here that has many tutorials. Some of which take you through the steps of setting up a members area. I an currently working with the code from one of their tutorials.
But BEWARE, if you are new to PHP then simple copying and pasting will not work. What is more is that the code is not perfect! I found several errors.
If the tutorials on phpfreaks.com are too complicated then I recommend you purchase 'PHP and MSQL Web Development' by Luke Welling and Laura Thomson ISBN 0-672-32525-X