Getting pretty sick and tired of hearing the same old 'modern idea' chestnut being trotted out once again. Who cares if it's a somewhat mix of modern ideas? In our world, we didn't have magic, and we didn't have things like Divine personifications of the Green coming to people and telling them 'It hurts when you do this, and here's how you can make it better for the both of us'. The reason we in this world didn't do it earlier was that we were ignorant of such things; we didn't have nature priests that could cast a spell and find out what the local ecosystem/spirits wanted to do.
The general take on Druids I use is this:
NG: They serve Nature. Man is a part of nature, as are his crops and fields. They actually work with farmers and orchard growers to make sure they use proper techniques that don't erode the soil unduly and show them how to safely deal with large amounts of concentrated animal waste. They bless the crops and animals, making sure they are healthy and strong. (This also puts them in good graces with the farmers; the farmers are more likely to listen to someone who ups the weight on his cattle, and do the extra work that the druid wants to see done).
They don't much like cities. Cities produce too much waste for the local ecosystem to absorb. They try to deal with it, by encouraging the city elders to spring for some means of dealing with the waste.
They try to curb roads being built where none are needed, and try to restrict building where it isn't needed. They try to make sure wildfires don't go out of control (since some fire is good for a forest), that too many of one type of animal doesn't dominate, etc; they are like a hand on the brakes, making sure everything rolls along at a smooth pace.
TN: These are the guys you have to watch out for. These druids don't much like intelligent creatures at all, at least the tool-using ones that shape nature to their desires rather than being shaped by it, and even the humans among them don't have a very human mindset. They are much more likely not to be human or humanoid themselves. They view any creature that tries to 'tame' nature with a distant disdain; they dislike humans and goblins alike. Elves they can deal with, since elves always take great care to built unobtrusive structures that blend in with nature, and show great reverence for it. Elves limiit their own numbers and don't multiply all out of control like the younger races. Halflings, too, they can usually get along with, as halflings move around a lot and take care not to leave a permanent mark on the area. But the elves and halflings still respect and fear them, because these druids aren't anyone's friend in much the same way that a thunderstorm or pit viper isn't anyones friend but can be dealt with if you are knowledgeable and lucky and willing to respect it.
They liked human better when they were cave dwelling hunter-gatherers and most TN druids want to see people not go past that stage. Farmers and folk near a druidic wood half-appreciate and half-fear the druids. They gather only fallen wood for fires, or do without; they farm in patches, rather than in furrows; they keep only a few animals, and those roam as they wish. Any meat they get, they have to hunt rather than raise. If they become too numerous, they send people away because they know if they do not, that a druid elder will come and cull the village down to a manageable size, like you do with any herd. These are your bloody-megalith-by-moonlight types. Hippies with huge scythes and savage wolverine companions.
I haven't worked out a great deal on evil druids. I usually see them as cut off from the divine power of nature itself and having turned to an evil forest-aspected spirit or minor god, or a spirit of disease and blight that is nature denied, or nature corrupted. There are not a lot of these at all, and they are hunted like dogs by both other druidic factions.
