Stack Exchange sites that have graduated can add community ads to the rotation of ads shown on the front page (that place where you sometimes see ads for random other SE sites). These ads are voted on by members of their communities, and if enough voters agree that the ad would be welcome on their site, it's added.
We already have some ads on other sites, thanks to Neil, but let's collect them all together in one place -- for community visibility, and because these ads have to be reposted each year so having one meta question here to work from will be helpful in the future.
Please use answers here to collect ads we've proposed on other sites, or ads you would like to propose on other sites. Indicate the site and, if it's been proposed, link to the proposal on the other site's meta.
Here's the required format for ad submissions:
The image that you create must be 220 x 250 pixels
Must be hosted through our standard image uploader (imgur)
Must be GIF or PNG No animated GIFs
Absolute limit on file size of 150 KB
All answers should be in the exact form of:
[![Tagline to show on mouseover]]
: http://image-url : http://clickthrough-url
The link could be to our main site, to a tag, or to a specific question.
Let's get ourselves some more publicity. Can you help?