The Treasury Inspector General for Tax Administration (TIGTA) has a website for reporting IRS impersonation scams - you know, the phone calls that threaten to have you arrested, sued, flogged etc. unless you pay up immediately.
Several of my clients have gotten these calls, and I just got one myself.
(I resisted the temptation to call back and demand my refund immediately...)
Don't know how much good it will do, but for those (like me) inclined to report such things, here it is: