Improvements:
- What can I barter? Why not show items available for bartering. I won't sign up unless I know what I'm signing up for - Navigation should always be on top even if it looks better somewhere else. User behavior trumps aesthetics in some cases - Remove the expanding buttons!!! It is very unintuitive! They do not need further explaining - About us page is very small. Go into more detail about yourself and the product. You need to gain trust as well as demonstrate clear goals for what your product is, why it is necessary, and so on.
The site needs lots of improvements. Try taking a look at other similar product categories and see what they are doing to fill their site and make it more polished.
It seems too bare for me personally and I wouldn't look into it further without examples of the product.