Researching mythical creatures and don't know where to look for info.?

I'm working on a fictional book that includes several "beings" that are magickal/mythical in nature. The problem for me has been in researching them. I want to be as accurate as possible in my portrayal of them, and even if you don't believe in any of them, there are still many established ideas and beliefs about them. Now, everytime I research a new one and I hit a wall, I send out an email to various groups hoping someone has some info for me. But I guess what I really want to know is, do any of you have any ideas as to where would be a good place to do the research on these beings? Whether it be online or in a book, I'm open to either one. Charts and other references like that are much more useful and definitely preferred. Now I'm open to what would be considered "factual" and what would be fantasy. I'm trying to find a happy medium between the two. So any ideas or nudges in any direction would be great. Here are the ones I still have yet to piece together resources for:

Angel

Demon (in the generic sense)

Leprechaun

Dragons (in particular the care of a baby dragon)

Succubus (although I might have enough for this one)

Brownie

Elf

Nymphs (specifically how many would commonly travel together, possibly going to use Dryads)

The one thing I need the most is lifespans, what their family/upbringing would be like, pretty much background info on them. And again, I am not asking anyone to do any work for me, I am just running into dead ends and need help knowing where to find the research at. Any assistance is greatly appreciated.

~Willow~