Do you have a fence? If so, you may need to use some wire mesh around the lower perimeter.
Here's what I'm going to try this year. Around the whole perimeter of my fence, I'm going to take chicken wire or a very small mesh and fold it length-wise so it forms a 45% angle. Then I'll attach it to the fence so that one side of the 45% is laying against the fence and the other side is laying on the ground (slipping this under the sod so mowing won't be a problem). It's really hard to explain so I hope you understand.
The goal is to prevent the damn rabbits from going through the wire (they can easily squeeze through a 2 inch gap) and to prevent them from nesting or digging under the fence. I also hope to prevent the dogs from digging around the perimeter too. When the rabbits around here start nesting, they always choose a spot right next to the fence (on the outside) and the dogs go berzerk trying to dig the baby bunnies out for snacks. I've written on this forum before about how disgusting the dogs are when they find a nest.
I've tried all the repellants and they don't work for me but that's another option you could try, too.
I've heard that tying aluminum pie tins to the fence will discourgage animals. One of my neighbors tried this on her house for woodpeckers and it was very effective but her next-door neighbor complained about the noise of the pie tin banging at night. She switched to mylar strips, however, I don't think that would discourage rabbits.
If you come across a good solution, be sure to let me know. This is a very big problem for me.