I have used just about all of the materials for tails already mentioned, but for me, I prefer spade hackle over just about anything else. There are exceptions, of course, but, generally that is what I use and would recommend. You guys who are going to the Sommerset Show should go by and visit Charlie Collins. He has bags of spade hackle for $5 that will provide all of the tailing material you will need and for me is the best thing to use for tails.
Sandfly, I must admit, I haven't used camel for tails. After being stationed in the middle east for 3 years back in the early 80's, I was sick and tired of seeing, smelling and eating camel. I never thought it could provide tying material! Maybe I will look at them in a different light now.
Cheers, Mike