Currently we have 4 300x250 ad spots left which are shown in the top post and every single post. These are in rotation and share ~400k impressions with 9 others. For just $75 your ad gets seen about 40,000 times per month. There are 3 text link ads spots available. Just $20 a piece. We do sponsored reviews for $200 a piece. These consist of 500+ words and 5 backlinks to your site. We also host sponsored competitions. In previous contests like this, we have had a great response and a boost in SERPs for the sponsors. www.johncow.com/advertise for more details.
The 300x250 spots are taken, there will be an opening for the 140x140 buttons in a few days, limited availability. $125 per month, ~400,000 impressions. PM me if you want to secure one.