I noticed an item in today's Sun-Times about this years rabbit population explosion. It gives some interesting theories that may explain why so many areas are seeing many more rabbits than usual.
I can tell you from my own experience that hardware cloth (heavy wire mesh) makes an effective rabbit barrier. I used it to build a cafe around my tiny Japanese maple when rabbits started eating it this spring. There is a similar product labeled "rabbit fence" which has the wires more closely spaced near the ground, also very effective. I used that around my veggie garden. Now I'm enjoying the veggies instead of the rabbits.
BTW, there is an effective repellent that the Sun-Times article doesn't mention: predator urine. This stuff isn't cheap, but it works. I picked up a container of coyote urine in a concentrated crystal form at the garden center and sprinkled it around planting areas that were not fenced off (didn't want to look at fences everywhere>. Every so often I reapply it. The rabbits are staying away.