ACG - I have a 3.5 mile ride as well and I also work in an office enviroment. Last year I commuted in my work clothes, but this year I've been wearing gym shorts and changing when I arrive. I have a collection of shoes that live at work so I don't have to bring shoes with me.
I do get sweaty because I push myself, but its not enough that I need a shower! (It's also why the original poster suggested wipes)

The booklet available (look at the website I posted above) does give some ideas on how to handle the whole coordination of clothes/sweat/etc and biking to work.