BuddyPress.org

I agree, Gravity Forms is well worth the money, even with the newish pricing scheme. The about-to-be-released 1.5 version even includes the option to replace the BP registration form and adds PayPal support and such (a developer license is needed for those). As far as I know there’s no inbuilt support for custom post types yet, but even using custom fields, coding a recipe plugin should be very easy.