Yes there is. It is near the bottom of the main page, immediately below the vendor section. The main page can be accessed by clicking on the banner on the top of every page.
You are required to be a Senior Member Plus (75 posts and having been a member for 15 days) to participate in the For Sale sections where all buy/sell/trade transactions are restricted to. The For Sale posting rules are in a 'sticky' at the top of the page in each of the 3 For Sale sections.