Here's two methods not yet discussed:
Microtransactions! These are the cheap extras that people can buy from within a game. These can be extra weapons, more maps or even just the other half of the game itself (treating the free offering as a demo version). There are three 'big' companies that make this easy for developers. Mochi's Coins make it very easy, but they take 40% and that is before 'costs'. FlashGameLicense do GamerSafe which has the same 40/60 split between them and the developer, but they have far, far less branding than Mochi. Mochi also forces the player to go to their site to buy Coins. Better, however, than both of these is Jambool's Social Gold which comes straight out of the Facebook microtransaction goldrush. There is no branding, users can buy your virtual currency straight in your game and you keep 90% of the profits. I'd use Social Gold if I were you. A few other notes, Sponsors hate microtransactions, so unless you have an awesome game, don't expect to get a good sponsorship while microtransactions are within your game. I think microtransactions work at their best when there is a multiplayer, or at least social, aspect to the game.
Self-publishing is a risky move, but it can pay off in the long term. This is where you host your games yourself. You are basically running a portal and revenue comes not just from in-game ads but from the ads scattered round the design of the site. Not a particularly nice option because you may have to spend a year or two just building an audience and having people return to your arcade daily. It's a massively competitive market too. On top of all that, administering that website really is a full time job and you'll probably do less game development as a result.
