Concerning Istaris

[lathspell]

Does he really help them besides caring for them from his home in Mirkwood? He did little to oppose Sauron.

Yes, he helped the Istari in many ways, though he was always on the background. Usually it was Gandalf who dealt with Sauron, and later also with Saruman. I think the best way of Radagast's help to the otehr Istari were his birds. All birds were his spies (except, I think, the Great Eagles and evil birds), and he gathered much news for the others.
In the Hobbit, when the dwarves of Dain and the Elves of Mirkwood are going to fight, Gandalf suddenly stand in the middle, saying that he has news that even the Elflords may not know. For he knew that Bolg was coming with many a warg and orc. I always suspected Radagast to be behind this information, from his birds or other spies. It was also the year that the Wise drove Sauron from Dol Guldur, so Radagast and Gandalf did meet in those times.

Well, I certainly don't think that the coming of Radagast was useless. He played a small part, but I think it was one that no one else could have played.

greetings,
lathspell