I heard about this site refreshlink.com on smartbloggerz. This is a site that lets you show your banners on their homepage for free. You don't even have to register and takes less than 3 minutes excluding the banner creation time. My first banner stayed on that blog for 3 days and generated up to 200 pageviews in total, but my second and the third banner moved out of the homepage in just 1 day, this is due to the increasing popularity of that site.
According to the owners this is the first of the kind service on the web, the owners make their money through the non-rotating banners, the free ad spaces are always being rotated and so there is always the availability of ad space.
This site was just recently started and is not very popular yet, so don't miss this oppurtunity. If you want to visit it click here.