Whats the best free membership plugin for wordpress?

I have been developing a website for a while now gaining returning visitors that like my content. I had been planning for a while now to make a membership section that members will have to pay to sign up. Basically I am just going to be posting a premium more in depth version of the content that I am already providing. I would like to have it set up so that I get paid monthly via paypal and have it be integrated into my current blog without having to change much around. Does anyone know of a wordpress plugin that you can do this with?

S2Member is the best for that I think. I use it a lot. It might seem to be complicated, but it isn't. Works fine with paypal.
Not allowed to post links here so just Google "S2Member" and download the free version.

Thank you for the referral to S2Member. I looked up the plugin's download page and it looks like a pretty useful one for what I have in mind. According to their site details, it includes the option to add buttons for PayPal, ClickBank, Google Checkout, and several others. What I really like is the affiliate management and tracking capabilities. It comes with both the free and paid versions, which is a big plus for marketers who want to build a team of affiliates without spending more upfront than they have to. I am definitely bookmarking this plugin for future use.

there is a profits theme floating around, does the job pretty well

This is not a free membership plugin, but I was impressed with its features and comments from users.