How to create a Firefox toolbar?

Is it hard?

[fischermx]

I have experience in Delphi and C#.
I'm lost in the firefox developer's page, without finding exactly how to create a toolbar.
I have no idea which language do you need to use to create a Firefox toolbar.
Does anybody has experience on this or has tried it?

[keyplyr]

Just in case you weren't aware of this group [forums.mozillazine.org], especially the development forum.