Railriders makes some great pants. I have a pair of their Backcountry Khakis that I wore to work throughout this year's hot and unusually humid Oklahoma summer (including during bike commutes). They look like a casual pair of khakis and dry incredibly quickly. They're also really durable.

Read comments for Railriders pants, though. Often their waists run quite large, and some of their other pants may be a little too outdoorsy for some workplaces.