I don't know about favorites, either. I donate to HSUS, although Pinkie has a good point about being local, and I've considered just sending my donations to the local shelter instead of HSUS. I've also donated to IMOM.org. My vet and I sent donations in Willow's name to a research/education center in Columbus, though I can't think of the name right now...I'll have to look that up. I've thought of donating regularly for FIP research in Willow's name, but have just given generalized donations to IMOM or HSUS instead.
My favorites are the ones I volunteer with!! Beagle Paws and Greyhound Pets of Atlantic Canada.I give them donations and I also give Ruff Spots donations (I used to volunteer with them too awhile back).
I ocasionally will donate to the SPCA,but mainly it is the ones above!!
I really like my local humane society.... I think the humane society in general is a good organization. Although with any large scale organization like HSUS there are probably going to be some things that they do that not everyone fully agrees with ... I love my local one, so if I was to judge the group on a whole based on my local chapter I would say HSUS (we do not have ASPCA here).
Non local??? Well then...I have not really supported alot of organizations out of my province.I did used to support a couple of rat organizations in the USA and also Greyhound Protection League,but have not supported any of them in a long time.