Turning an extract from a movie into an animated GIF?

Hi,

I'd like to turn an extract of a movie into an animated GIF. What's the easiest and best way to do it on Mac? I searched the internet but didn't find anything useful ...

Also what is the best (free?) software to extract a scene from an AVI, MKV, etc in the first place?

Sorry for the noob questions

Thanks a lot!

Jerome

Thanks but that still seems extremely tedious ... ?

Does the GIFBuilder only accept GIFs? That would mean I had to save each frame manually!?

Isn't there a program that converts an AVI into GIFs?

Thank you.

ps. Stupid question but do you know if there are easier way to do this on Windows?