The Internet Movie Database is the best resource on the Internet for information about Films and Television. For the most part, their web site is great but some of the pictures in the cast list are a bit small and difficult to see.
Most of the time the actors and actresses profile photo is a pretty clear head and shoulders press shot which has been shrunk down to 32x144. There are, however, many not so famous actresses (and actors) whose profile photos are just grainy black and white photographs of them on set or shots of them in a film. After they have been miniaturized they are unrecognisable.
I really missed the Facebook style pop ups you get when you hover over someone's face. So I wrote a Greasemonkey script to fix it. Install the script and go to IMDB, look at the details of a film and hover over the image next to the persons name. The face will be enlarged with more detail and overlaid in the centre of the screen.