Hey, thanks!
I second the request; this advice is great! I have two cats and was planning to go car-free again, figuring I could rent a car for their [rare] vet visits, etc. However, five days before my car was due to be picked up, I heard this funny noise outside my window...
It turned out to be a starving, malnourished, pest-and-disease-ridden puppy. Naturally after the vet visits, the carpet spots, the sopping towels, and the 3 am trips outside to urge him to "Go potty for Mommy!", I couldn't give him up. I'd been racking my brain for ways to transport him on (or behind) my bike. I think he's going to max out at 40-50 lbs, so he could ride in most child trailers (yes?).
This info was very helpful; any other suggestions would be great, too!