Good job, keep it up! As others have said, keep stuff at work so you don't have to lug it around every day (even if it means driving in once in a while - that's okay!).

You'll want to look into fenders soon - looks like your bike has enough clearance for "full length" fenders. Even if you don't plan on riding in crappy weather it has a tendency to catch you by surprise, and fenders will make your commute much more pleasant!

And as the days are getting shorter, you're going to be commuting in the dark soon (if not already). More lights! Always more lights!

But most of all, have fun! My days always seem better when I commute by bike, because instead of stuck in traffic or on the subway - hey, I got to go for a bike ride!