Local and collector streets, arterial roads in city centre. Sometimes bikepaths.
Prefer to get to/from work human-powered - bike or run. Also getting into biking more seriously as a sport, so use commute time to train. i've recently converted to a road-geometry bike with skinny tires, and actually prefer its lightness and responsiveness even if it's sometimes jarring!
The more I commute by bike the fewer close calls I have.