As co-Programme Chair for SPA conference I often find myself trying to persuade inexperienced or completely new speakers that it is worth doing and that they have something great to say. Here are some of the resources that I send on to them.
Nicely expressed post – you don't have to wait to be an expert in something before you submit a talk: You can speak at a conference too.
More detail as to why what you have to say is worth hearing, and how to get started. So Why Should I Speak Publicly?
The list of accepted talks from last year's PyCon US is a long list of great-looking talks on a variety of subjects to spark ideas of what you might speak about.
If you are nervous about public speaking, this post could really change the way you think about it: Presentation Skills Considered Harmful. You are just the UI.