Practical cleaning routine for a commuter bike
Overview
As needed or as inspired, rinse off bike with water, clean with soapy water and degreaser, wipe down, rinse off. In practice, I do this every month or two or... of commuting. And yes, there are advantages to cleaning your bike; a clean bike will last longer, perform better, and serve as proof of the love of a proud owner.
Materials

rags
sponges
bucket filled with warm water and soap
scrub brush with plastic bristles
simple green or citri-solve in spray bottle
lube

Methods

Rinse bike off with water
Liberally apply soapy water to entire bike with sponge
Wipe dirt off everywhere except drivetrain with sponge
Wipe dirt off drivetrain with a dedicated greasy sponge
spray drivetrain with degreaser
wipe down drivetrain with rag
rinse again
apply lube to drivetrain
remove excess lube with rag

Notes
this answer focuses on cleaning the bike, but cleaning is also a good opportunity to check the bike for mechanical issues, including worn or loose parts:

tires
brakes
bolts
all other parts, including frame