I used to either wear my running shorts in the summer or whatever pants I would be wearing to work that day on my commute in the winter. Though since I've gotten some good biking shorts I do prefer wearing those instead on my commute to work (this is possible because my office has changing rooms and stuff for bike commuters) and it's simply just that much more comfortable for me. I definitely had to get over insecurity of "looking like one of those lycra guys" but honestly, good bike shorts are a good investment period. The one thing I have yet to invest in personally are waterproof pants for cycling in the rain. If you're a commuter who bikes rain or shine that might be where your money is best spent too.