Statistically speaking, Fri and Sat tend to be the best days to play and Mon and Tues the worst but it is really about table selection. Some of my best nights ever have been a Tuesday night (twice) and a Wednesday night.
I often times take a shot on the "slow" nights and see if there are any good tables. The upside is that there are less pros out these nights so it could work out in your favor.
The opposite holds true too. I've had several frustrating Friday and Saturdays where I kept changing tables but could never find a good table for me. It used to frustrate me since I felt that I was wasting a prime night but I now know that it is a numbers game. It's always worth going out and switching tables a few times to try and find a great game. You have nothing to lose but your time.
friday saturday and sunday are peak. Friday night esp is pretty lolz sometimes.
monday and thuesday are dry cause they are following a peak/bankroll crash that will have to wait til the next thursday. for most rec players at least.