In the Arizona Adventures campaign, druids are part of an ever-present network that can be found, and that CAN FIND YOU, pretty much anywhere you go in the wilderness. I think of the druid network as a group of self-appointed "park rangers", and they view the whole state as their park.
[Suddenly and surprisingly, from behind a tree a man steps out, mostly naked, with wild dreadlocked hair and dark sun-baked skin. He raises his hand in greeting, and says, "Hi, I'm Druid Bob, welcome to the Coconino National Forest Preserve. We invite you to enjoy your visit to our forest, and would like to kindly remind you to be a respectful visitor by picking up all garbage as you travel. The fire danger level is code red this week, so please, no campfires in the forest; remember, only you can prevent forest fires..."]
They are absolute masters of the terrain, and pretty much know everything there is to know about the monsters and humans in any area. They are likely to be keeping tabs on any intruders, probably in an unobtrusive animal form.
Depending on the actions and attitudes of the PCs, the local druids can either be guardian angels or avenging angels:
--A druid might help the PCs out of a tight spot, or provide them with some saving resource.
--A druid might reveal to the party a crucial piece of information about the area, like monster lair locations, or dungeon entrances.
--A druid might also attempt to recruit the PCs into an adventuring hook, like asking the PCs to take care of an intruding magic user who has been upsetting the balance of nature lately with his monster summoning and wacky experiments.
--If the PCs are the cause of the disturbance, or decide to disregard the "park rules", a druid may become the party's hostile stalker...
In Arizona Adventures, the druids maintain a headquarters of sorts in the area of Fountain Hills (south of the Tonto Forest, at the NE edge of the Phoenix valley), tending the sacred fountain there. They are the only group to be trusted by and have a positive relationship with the Elves of the Tonto Forest.
They also maintain a permanent liaison in Tempe to consult with and advise the Arya leaders there. The druids are privy to an widereaching network of knowledge, extending even outside the Arizona region, and so their counsel is well-regarded and highly sought-after. Their yearly blessing upon the domesticated animals and crops is also highly valued.
In return for the druids' services, the Arya leaders have agreed to recognized Celt sovereignty over the wilderness regions, and to seek the druid's permits for any major activities there. The Arya leaders also agree to send their clerics and fighters to combat any undead which make their way into the druid's wild lands.