I have been posting this response for a few years now on these types of threads, and I swear I am not a spammer for patagonia...
I am not very competitive anymore, although I once was rather good in college. I live on the West Coast, so I am not sure if the East Coasters can do this type of thing, but it is worth a try.
Go to Patagonia, or get their catalog and look at their running packs. They make one called the Houdini Pack that is basically weightless. It has room for one outfit, and some necessities like keys, wallet, etc.
Here is what I do...
I keep a pair of brown shoes and a pair of black shoes at the office, under my desk. Everyday, I get up, brush my teet, shave, throw on my running clothes and pack a pair of suit pants/khakis, underwear, socks and an oxford shirt into my Houdini Pack. It then weighs like 5 pounds. I put it on, and I run 8 miles to work. It takes just under an hour. Driving, it would take me at least 45 minutes and I would have to pay $14 a day to park my car.
Instead, I pay $50 a month to join a gym across the street and end my run there, shower, hang my shorts and shirt in the locker and take my bag and running shoes with me to the office. I start work around 8:00-8:30am.
At the office, I choose the appropriate pair of dress shoes and leave my running shoes in a closet across the hall that no one has ever opened except me.
At 5:30-6:00pm, I take off my office shoes and leave them under the desk, grab my running shoes and take my bag back to the gym, get back into my smelly running clothes (dry by this point) and re-pack my office clothes into the bag. I run the 8 miles home and get home MUCH sooner than I would driving.
I do my long run on Sunday, and since i don't really do track work much anymore, it is kind of a non-issue. If I did still do it, I would just hit the track I pass on the way home.
I have been doing this almost daily for 4 years. My average is about 115 miles a week and I can honestly say it feels much easier than the 90 mile weeks I used to put in during college, post-college, etc.
Some evenings I go out with work folks, and just cab home, but most of the time if I have plans, I get home quicker running anyway, and just take a quick shower and meet friends after the PM run.
I see more of my family since running just replaced my commute, and now I don't need to go after work. i get home by like 7:00-7:30 every night and get to hang out with the kids and everything.
I am not saying I am special, but just pointing out that if you are creative, and look at your options, it is actually pretty easy. I had no idea how close I was to the office until I tried running one day. I just presumed it was like 20 miles b/c of the way I had to drive. Google Maps helped me a little, but basically one morning I just made a B-Line for the office and realized it wasn't very far.
Best to everyone out there.