I'm thinking about trying kongregate, and they're monthly compos. You will not become a millionaire, but money might roll in - at least this is what i've read.
Another option im looking into is the MarketJS, and selling games to publishers. If i focus entirely on this, i could probably push out a product each month, or every 2nd month. Of course, if i manage to maintain superb quality, and deliver polished products, there might be thousands of dollars on exclusive/non-exclusive contracts, and additional income on ads.
I'll probably exclude Facebook for now, as i would need alot of features to be working in harmony with the facebook API. I just dont see "kongregate-type" games on facebook making any money stand-alone.
When it comes to mobile, iOS and Android, i'm really just waiting for it to be stable enough - and even then its a lottery. You might sit on the greatest game of all time, but you still might end up on the bottom, never to be seen on the market.
Another option is Steam, and the greenlight stuff. But its far-fetched in my eyes at this point, and the scope of the game should then be much, much bigger.
So uhm.. TLDR; Personally, I'd go with kongregate, or MarketJS (selling to publishers) in order to monetize, while still being on the lookout for iOS/Android and standalone options.