The Subscription Module Add-on with PayPal allows WP-Members to limit a user to a specific subscription period and allows you to charge for subscriptions using PayPal’s IPN.
Version 0.1 (requires WP-Members 2.8.x)
Version 0.2 (requires WP-Members 2.8.x)
The new 0.2 release offers an option for recurring payments and an improved admin interface. You also no longer need to add functions for wpmem_post_register_data and wpmem_payment_button filters. These are built into the plugin. However, if you want a payment button to display in your successful registration message, you do need to add that via a wpmem_msg_dialog filter as described in the filters for 0.1 (You don’t need to do this if you are offering a free trial period).