Since my previous spam filtering system was wonkier than wonky, I decided to give TypePad AntiSpam a try. The service looks sufficient and I've heard it should work quite ok. It has given already one false positive today, so it's not perfect. But every mistake will teach the system and improve it, at least that's what they promise.
Now before you even say Akismet, I've got to tell you I cannot afford to pay 50 USD a month at the moment. That's the price for multiple sites (I have two) which run ads and/or are promoting a product or a service. I'm sure Akismet is all sorts of awesome and some are totally in love with it. It's just not an option. I sort of like the statement TypePad makes about their AntiSpam: "We don't make money from spam!"