Dynamic Drive have a number of these navigation menus, and if I remember correctly some/most of them have Opera support.
It's always a good idea to do some research into how these work and how to achieve this effect. Often, people find out that it's quite straight forward to do yourself, and you cut down on quite a bit of unnecessary code (it's there in the free scripts to make it easy for people to customise).
If you do have a go at it yourself, don't worry! If you're in trouble there are plenty of people here to answer your question!