Before you rehome your rabbit consider whether it is really necessary to do so. There are many different reasons why people need to rehome their rabbit(s) but sometimes there are other solutions.
Lets look at some common reasons and their solutions...
"I'm moving house and won't have a garden." - Why not move your rabbit inside. You can buy very pleasent looking inside hutches/cages or make your own. Rabbits adapt very well to living inside.
"I /My partner/ my child is allergic to the rabbit." - First check that it's the rabbit itself that's causing the allergy. Bedding such as straw and sawdust or cleaning fluids could be the problem, and there are alternatives to these. You could also talk to your doctor, who may be able to prescribe medicine to control the allergy. More frequent cleaning/grooming regimes may also help lesson the allergy.
Pet Health Council - Pets and Allergies Leaflet
"He/she has behaviour problems." - Bahaviour problems can often be resolved. See Problem Rabbits.