I have a pair of lightweight sport pants from REI that I like to wear over my shorts, they work out very nicely for cooler days. They have zippers on the back seams at the ankles which allow them to fit close enough not catch on the chainring and also makes it easy to take them off while you have your cycling shoes on. And they're not form-fitting, which makes it a bit easier for people like me to wear them out in public

http://www.rei.com/product/47625343....S_CLOTHING_TOC

I also plan to get a pair of warmer tights for when the weather starts turning colder.

I prefer pants/tights without the chamois pad so I can wear them over my regular cycling shorts, that would let me take them off in case the weather turns warmer than I expected.