Kohls has some good ones. My sister (Doctor, professor, mom of 2 young boys) swears by Betabrand (essentially feel like yoga pants but look dressy). I wear a uniform or else I'd be all over those.
I plan to wear maternity pants for a few more months. More in the heavy jeggings category, so it depends how casual your work environment is, but my mom gave me some ponte pants from Costco and I got some old navy rockstar jeggings that I love. Both are much heavier material than regular leggings, and have faux front pockets/stitching and real back pockets.