Hi all,
I've just created a free payment plugin - Pmints Payment. It is a social payment plugin; it lets your customers pay for your products by mean of a Twitter or Facebook posts. In other words, you are giving free products in exchange of social mentions. This plugin is a payment plugin, and when activated will be listed as one of the payment method during checkout.
The plugin uses Redirection method; your customers will be directed to Pmints website to make "payment" (share your post). You need to create an account on Pmints.
Please read more about the plugin at http://www.pronopcommerce.com/pmints-payment-nopcommerce-social-payment-plugin.
Please also feel free to visit my blog at http://www.pronopcommerce.com. I'll be constantly creating free tutorials on plugins and themes development, and I'll be giving away free plugins from time to time! :)