Comment by nostromo

Here's a good write-up on how to see if your company is listening in on your encrypted web traffic:

http://security.stackexchange.com/a/2920

(Note: MITM is just one way companies monitor employees, but by no means the only way. If your company provided your work computer to you, or if they installed anything on your BYOD computer, I would treat everything you do on that computer as cc'ed to your boss by default.)