Testing Sound/Video Sync

I noticed this morning (and sometimes in the past) that the sound and the video on my TV doesn't always sync properly...maybe I'm crazy, but it seems like a second off. i never really noticed it that much but today I was watching something and the person hit the palm of their hand with their fist and the sound occurred before the fist hit.....does anyone know of a test that can be done (or a movie clip) that would be a good test for this type of thing?

What is the source of this Video?
Cable
Sat
DVD
VHS
DVR
PC hooked to TV playing video's?
If it's a PC what program are you using to play the file? What is the file type? Download GSpot to get info about the video clip. What Codec Pack are you using (DefilerPak is the best)?

I have many clips and only a few are out of sync. Good programs will let you change the audio offset + or -