I still go the ghetto route.
I have a bungee net ($3 at ocean state job lot) and and an cheep skateboard backpack ($15 at wally-mart).
I use the buckles on the back to keep a bungee net attached to the backpack and then bungee it to the passenger seat. Used to carry it on my back but realized it blocked the air vents on the back of my jacket, and also when carrying all my work crap could cause fatigue on long rides.
Works out well because it allows me to quickly and easily stow my jacket in the bag and walk around with all my gear while my bike is parked. Just a thought for newbies who are a little strapped for cash.