Another vote for a donation/subscription based model here.
Have you also considered something akin to Joe Saward’s GP+ magazine? Where he has his blog (and The Mole) which he maintains for free, but after every race he releases an e-magazine for subscribers only. It only costs £30 a year, and it’s full of interesting content so I’ve been more than happy to subscribe. I’m sure you could pull off something similar.
I also suspect that he hasn’t really tapped into the ‘App’ market, and I’m sure there’s a LOT of potential for releasing a magazine straight to Ipad/Android/Kindle, which could rake in some considerable money. I downloaded GP+ to my tablet, and it is a great medium on which to consume that sort of content.
With the wide reach this site affords you, it would be easy to generate publicity for it.