Well here's a really simple script that you can use to block all access to the context menu (not just from the right mouse button but from the keyboard as well) and really annoy your visitors. The script is even simpler than most of the ones that only block the mouse button and works in about as many browsers as those scripts do. Here's the entire script for you.
Adding just that small piece of code to the body tag of your web page is more effective at blocking your visitor's access to the context menu than the many no right click scripts that you can find elsewhere on the web because it blocks access from both the mouse button and the keyboard options described above.
Of course the script doesn't work in all web browsers (eg Opera ignores it - but then Opera ignores all of the no right click scripts as well).