The main thing I do is ride the bus combined with biking. The bus has a bike rack on the front, so I ride my bike to the stop, put the bike on the bus rack, then, when I get off the bus, I ride the rest of the way to my destination.
I like the idea of adding the cost to the equation. What about adding in the environmental impact, too? For me, both of those are important. I use Google Maps to plan my trips, and am disappointed that I can't create multi-modal directions.