It’s not too unusual for bloggers to run contests in attempt to raise their PageRank/Technorati Authority. You may have considered this briefly, but dismissed the idea when you couldn’t think of anything good to offer as a prize. Here’s a possible solution: Refurbished iPods. Apple will sell you iPods that have been returned (and fixed) for about $50 less than the list price. There’s nothing wrong with them, so they’re a great deal.
A refurbished iPod Shuffle costs $50, and a 2GB iPod Nano $100.
A lot of people don’t know about the refurbs, because Apple buries the link on their website.