A fellow cyclist who is also a runner mentioned to me that she used whey protein that is available at big box stores. As she follows the advice of a nutritionist, I thought I'd give it a try.

I use it occasionally as I've heard that your muscles are craving protein after a ride. I mix it with 1% fat milk with a hand blender.

It does appear to help me recover. For example, on Mondays I ride solo in the morning and with our bike club in the evening. After the morning ride, I have a glass of whey protein/milk. Following this regimen, I'm usually good-to-go for the evening ride. Typically, the evening ride with the group is faster than my morning ride. I tend to use it after long and/or hard rides as well.