
The application is fairly well hidden (which is what makes this a hint!), but you can find it here: /System » Library » CoreServices » Screen Sharing.app. I suggest making a dock shortcut to it.
[robg adds: An anonymous contributor also pointed out that you can access the program via the Finder's Go » Go to Server menu. Choose that, and type vnc://1.2.3.4 in the input box, where 1.2.3.4 is the computer's IP address or DNS name. Screen Sharing will launch and prompt you for a password.]