In my prenatal yoga classes, we always take a tennis ball & rapidly roll our bare foot back and forth on it. It is heaven. I think this would be good for anyone - pregnant or not, after a long day of walking or on their feet. You can also get a good stretch by placing one heel on the tennis ball and pushing down with your weight. Then, alternate your feet. We also use this time to stretch your arms overhead and lean them to the left, then right.
I had been doing this at home on occasion, until I noticed that Zeus & Zoe kept taking the tennis balls as their own toys (because obviously they don't have enough toys of their own). Just doesn't have the same effect when covered in dog slobber. I may just need to stick to this exercise at yoga from now on.