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.