Sometimes you just need to take a day off. Maybe ride Monday-Tuesday and Thursday-Friday and take Wednesday off. If you don't want to take a day off, leave earlier every other day and ride at a gentler pace to massage the stiffness out.
Massage can help with specific tight spots.
Swimming is a good recovery exercise because the pressure of cool water on your body squeezes your lymph glands and drains them. Drink lots of water afterward. In fact, drink more water, period.
Mild over the counter anti-inflammatory drugs like ASA and Ibuprofin can help. So can foods rich in minerals like magnesium and potassium. (Dark green leafies, nuts, oatmeal, blackstrap molassess, etc.)