Well, when I was much younger than my 54 years of today, I used to bike commute and did so for almost a decade. Some things I learned are all here.....antiperspirant left at work, change of undergarments at work, etc.
Get a flat repair kit.....you'll regret it if you don't. Hell when the flat finally happens and costs you so much time walking in that you miss that important meeting.....I carried two tubes, flat repair kit, and a CO2 gun/head and two of the large CO2 carts. While CO2 is not a permanent fix for flats, it is quick and great for using for a day.......
Slime can be great, but as noted it adds a lot of weight and does make a difference in your riding experience. And, as was noted, slime is rather worthless for pinch flats. And many times, you find two holes with pinch flats, matching both rim edges......tire flattens out and pinches the tube on both sides. Gives a very distinct pair of holes on tube. But you tend to see more pinch flats in mtn. bike tubes than road bike tubes.....lower air pressure in the mtn. bike tires/tubes.
I started out commuting on a mtn. bike and quickly moved to a road bike. Difference was night and day between the two.....and I had my mtn. bike equipped with some Continental mtn. bike high pressure slicks.....think they were the Grand Prix (I don't think they're made any more, but other companies like Kenda and Specialized make essentially the same thing), 26 x 1 and around 100psi.
Also, give yourself some time to adjust to commuting.....at first, you'll sweat like never before and if haven't ridden distance like that before, hurt in places like neck, etc. A month later, sweating is much reduced and no more pain.....body adjusts.
And you'll soon discover some of the "minor" roads that most car traffic ignores.....and end up getting across town faster than cars.
Lot of good cycling etailers out there........
http://www.jensonusa.com/ <---great site, watch for sales!
http://www.pricepoint.com/ <---another good site, decent prices
http://www.coloradocyclist.com/home/ <---good etailer, but more expensive like Nashbar and Performance.
http://www.cambriabike.com/ <---one of my favorite places...great prices!
http://www.thethirdhand.com/ <----the place for any/all small parts you'd ever need