Have you ever been watching a show, and one of the actors looks so familiar, but you just can't place him? This happens to me a lot. I'm much better at faces than I am names. (This is not a great attribute for someone getting a history degree, as I did in my pre-children days. History is stocked with many, many more names than it has faces to go with them.)
This used to drive me crazy. What had I seen her in before? It would haunt me for days, like something left undone on my to-do list. Clean the bathroom: check! Go grocery shopping: check! Figure out who that gal was on the movie we rented the other night: ARG!
But a few years ago I discovered this site: The Internet Movie Database. The name is misleading, because they also have television shows and actors on there as well. In this database, movies (or shows) and actors, producers, directors, etc. are cross-referenced. This has saved me from the perpetual state of what-have-I-seen-him-in-before-ness.
Let's say you've seen the guy in the latest Star Trek movie before but can't place him (I haven't seen this movie yet, but am trying to figure out when I can before I leave town for Thanksgiving!). You can look up "Star Trek" on the imdb site, and click on the 2009 movie. This will take you to the page for that movie. If you scroll down to the characters, you can find the list of actors and the characters they portrayed. Click on the actor you are trying to place and you'll see the list of everything he's been in. The guy that plays the young James T. Kirk? His name is Chris Pine, and he starred in... Princess Diaries 2! Aha!
Don't you just love the internet? Anything that helps relieve my mental anguish over puzzles I can't solve is tops in my book. So next time you are stumped, you know where to look.