Google just added the ability to look at typical traffic on a particular day and time, in addition to live traffic. It's really an incredible feature. You can zoom into the city you want to look at, then choose any day of the week, and any time from 5am to 9pm to see what the historic traffic pattern has been.
Here's an animated image I put together that shows the traffic around Louisville for a typical Wednesday:
It's like magic!
Looks like traffic delays start around 6:30am, clear up, then there are issues from lunch till about 6:30pm, at which point it clears up. Try it out for yourself!