The following is an excerpt from Petfinder's FurKeeps Kickoff Ask the Experts Forum.
Q: I am thinking of getting pets in addition to my dwarf rabbit. I have had other pets before (guinea pig, chinchilla, ferret) at different points in time. My question is, do any of these pets tend to get along better than others?
I like to give them plenty of out-of-cage time and would like it if everyone could get along.
A: My expertise is rabbits and limited on the other animals you mentioned, but here's my two cents:
Rabbits are social creatures and would likely enjoy the company of another furry friend. However, introducing a new animal is not always easy. If you are open to it, I'd suggest considering another rabbit to be a companion to your current rabbit. They could keep each other company while you are at work, asleep, etc. Plus, there is really nothing like the cuteness of watching them cuddle and groom each other.
The kicker is, getting two single bunnies to become friends is a fair amount of work and takes time (although I'm sure that is true to some degree with all introductions between animals, regardless of species). I'd suggest reading more on the bonding process starting with the Minnesota Companion Rabbit Society's article, "Bunny Bonding Basics." I'd also suggest seeing if there is a rabbit group or shelter in your area that can help you with introductions. We recommend the equivalent of "speed dating" for rabbits to meet a series of potential companions and narrow it down to the ones most compatible.
If you'd rather have a different species than rabbit, there are pros/cons to those choices as well. Ferrets are natural predators to rabbits and I've not heard of anyone who has both and is able to let them play together. Guinea pigs and rabbits can make good companions, but rabbits are bigger and can inadvertently injure a guinea pig. Plus, guinea pig lovers will tell you that rabbits are carriers for bordatella, a disease that can be fatal to guinea pigs.
However, having said that, I know of several people who have successfully had rabbit/guinea pig combos -- including a Flemish Giant/guinea pig pair in which the guinea pig was the boss!
I don't know enough about chinchillas to comment on whether they could potentially play with rabbits.