I don't like the idea that druids have 'patron deities' in the same way as clerics. No thanks - that's cleric stuff (and not much to my liking for them anyway). This was one of my beefs with the Greyhawk setting - though there's plenty of other things I do like about the setting.
No, druids retain the old ways - which is to say a belief system (and source of power) more cthonic, deistic... to them, the forces of the universe are not anthropomorphic - I like to consider them to be perhaps more Nietzschean (in the "beyond good and evil" sense), not seeking a balance between good/evil, law/chaos - just disregarding them as meaningful constructs whatsoever. Where druids interact with society, I like to play them as chroniclers and overseers of oaths and pacts - where they are rulers they apply reason evenly, but rarely are rulers.
In my effort to not be quite so consumed by the internet and to read physical books more regularly again, I lit upon a book called "The Druids" by Peter Berresford Ellis which was a good read, an attempt to examine the role(s) druids played in their time, while admitting the representation historically skewed by Roman conquerers and Christian converters... I thought it was an interesting read. In general it portrayed druids as taking on a number of important social roles, moreso than overtly religious duties (though reliable details of druidic cosmology/philosophy/etc are few and far between).
(I could not find much critical assessment of this book on the web, but here's a page that someone put up - a review which I find myself largely in agreement with.)
The AD&D druid has always been one of my favorite classes to play, but one I've always wanted to find a better fit for when thinking about settings and campaigns and such. Still working on it.