The freecsscart.com has updated again, they are now offering sponsorship for $100 a month, its first come first serve:
If you are interested in sponsoring freeCSScart and the development process, we will give you a front page sponsorship advertisement image sizing in at 150×75 pixels. The advertisement will cost $100 a month. We are only allowing 3 ads, so first come first serve.
All info can be found on the freecsscart.com website.