Oooo viggen, that's a good one! Thank you for sharing that. :)
Here's one that merely costs pennies but will reward with site growth, particularly if you run a community. Advertise on "niche + blogs" so that publishers of sites trying to rank for that phrase or looking for link partners related to that phrase will find your site. Have the ad link to a page that discusses blogs in that niche. If you operate a community it's a good way to encourage knowledgeable people to join and become assets to your site as well as pick up visitors to their sites (with every post).