For a few months now I have steadily gotten money from a banners company. They really do not care how many visitors your have or if you PageRank went down last update.
They care about the quality of the site and if it fits their interest of advertisers. Last night I got two more sites approved so that means I will be getting $30 dollar a month from now on.
Maybe not the best payout but since they pay steadily every month and I have a lot of sites I consider it a good side income.
It is off course free to signup and ask if your site would get approved it only takes 48 hours or less.