To be honest, I get most of my inspiration from science media - books, documentaries, websites, and DVDs - and from learning in general. For philosophers, for example, I'd pick Epicurus, Democritus, Archimedes, and Socrates. Jeremy Bentham is the only contemporary philosopher I can think of off the top of my head.

Here's a couple from Epicurus.

It is impossible to live a pleasant life without living wisely and honorably and justly, and it is impossible to live wisely and honorably and justly without living pleasantly.

Epicurus

Don't fear god.

Don't worry about death.

What is good is easy to get.

What is terrible is easy to endure.

Epicurus

Watching a BBC Attenborough documentary is inspiration in itself, and strangely Douglas Adams' writings can be inspiring too - he had a new way of looking at things. He makes humour sublime.

For scientific writers, I'd pick Richard Feynman (with the advantage of being self-deprecatingly funny), Stephen Jay Gould (when he's at his best), Carl Sagan, and William Hamilton. There are many more, but I've only read extracts of their work.

I'm not sure you can have an inspiring atheist without drawing on some other view. The obvious ones are anti-theism or anti-religion, but the really inspiring stuff is pro-something, like pro-science, pro-existentialist, or pro-consequentialist.