Marketplace feature / selling single items

Hi,
I'm working on a project with Marketpress on Multisite Network and looked at this website in your 'featured' section http://teatra.de/market/

Can you please tell me how they created the 'Marketplace' layout and also if you go to the link above and click 'start selling' - that is incredible - how can I add that feature where people can sell a single item and just register with their paypal account??

These are great features!

Thanks

Rooze