3 Bunnies Rabbit Rescue is one of the rescues in my local area, and their website is incredibly informative! Their feeding tips are wonderful, and can be found at the following link...
http://www.3bunnies.org/feeding.htm
Just for the sake of convenience, I'll post some highlights of information from that website here as well...
The proper food will keep your bunnies happy and healthy for a long time. You must provide the following to maintain a proper diet for your bunnies: unlimited hay, especially timothy (except for alfalfa, which should not be given to adult rabbits in any quantity because of the calcium content); a variety of at least 3 green vegetables (see list below); some pellets (depending on bunny's age); a small amount of fruit and treats.
Do not let your bunny dictate what foods to give. Bunnies will eat foods that taste really good to them but are really bad for them. They don't understand proper bunny nutrition - that is up to you, in order for your bunnies to live long healthy lives.
Note: this list may not be as complete as it needs to be - when in doubt, don't feed it to your bunny!!
Adult rabbits should only be given a limited amount of pellets, but an unlimited amount of hay for the fiber and to help grind down the ever-growing front teeth. When rabbits are fed too much pelleted food, they will fill up on that and not get enough hay and grasses in their diet.
The following greens may be given to your rabbits (make sure there are no pesticides and wash thoroughly):
Alfalfa sprouts
Apple Mint
Basil
Beet Greens
Bok Choy (Chinese cabbage)
Broccoli leaves and stems (Note: broccoli can cause gas in some bunnies, and it is high in calcium, so it should not be given to bunnies who have any urinary tract problems, such as bladder sludge)
Brussels sprouts
Carrot tops
Celery (especially the leaf) (Note: to avoid any potential problems, slice or chop the celery against the grain so the veins aren't stringy - veins can be swallowed without proper chewing and can cause serious gastrointestinal problems)
Chard
Cilantro (no roots)
Clover & clover sprouts
Collard greens
Dandelion greens & flowers
Dill
Endive
Escarole
Fennel
Green pepper
Lettuce: romaine (only limited amounts, may cause excess cecals), green leaf, red leaf (no iceberg)
Mint
Mustard greens
Parsley
Peapods (flat)
Peppermint leaves
Pineapple-mint
Pineapple-sage
Radicchio
Radish sprouts & tops
Raspberry leaves
Sweet potatoes
Turnip greens (tops)
Watercress
Wheat grass
Some tips on keeping and serving greens:
-Always wash veggies thoroughly and dry before storing
-Get rid of any part of the greens you wouldn't eat
-Serve greens nice and wet to help with hydration and prevention of urinary tract problems
-To revitalize wilted greens, soak in water for a few hours
The following fruits may be fed to your rabbit in small quantities:
Apple
Banana
Blueberry
Craisin
Melon
Papaya
Peach
Pear
Plum
Pineapple
Pumpkin
Raisin
Raspberry
Strawberries
Foods to feed only in small quantities:
Carrots (high sugar content)
Kale (high in calcium, also may cause gas)
Spinach (high in calcium)
Foods to avoid feeding your rabbit:
Beets (sugary)
Breakfast cereals
Chocolate (NEVER give this to any pet - it is poisonous to most)
Fresh corn
Fresh peas
Grains
Green beans (can cause gas)
Iceberg lettuce (and any light green lettuce leaves, may cause diahrrea)
Legumes
Nuts
Onions (see this page)
Pelleted food with seeds mixed in (it's a treat to the bunnies but the seeds cause stomach problems)
Potatoes (white or red)
Seeds of any kind
Sugar, in any form
Foods that contain compounds that destroy nutrients:
Sweet potato
Cassava
Bamboo shoots
Maize
Lima beans
Millet
Bracken fern
Tea leaves
Coffee plants
Foods that are toxic to rabbits:
Note: do not allow your rabbit to eat dried leaves from any trees - too many types are very toxic and some can cause cyanide poisoning (this includes specifically apple tree leaves, oak leaves, maple leaves, etc). If you allow your rabbit an outdoor run, please clear the area of leaves as the rabbit may find them very tasty, but they are very dangerous!! (see also this page on cyanide poisoning)
Generally toxic:
Rhubarb leaves
Raw lima, kidney or soy beans
Onions
Citrus peels
Oxalates (causes pain and swelling of mouth and throat, swollen tissue can restrict breathing or cause suffocation.)
Begonia
Caladium
Calla lily
Diffenbachia
Dumbcane
Jack in the pulpit
Philodendron
Schefflera
Minor Toxicities (causes vomiting, diarrhea, nausea)
Aloe vera
Amaryllis
Bird of paradise
Birch
Boxwood
Cedar
Chrysanthemum
Daffodil
Daisy
Eucalyptus
Galiola
Hydrangea
Haycinth
Iris
Juniper
Redwood tree
Rananculus
Sweet pea
Swwet william
Violas
Extremely Toxic (one leaf can kill)
Angels Trumpet
Azalea
Black Acacia and Locast
Bleeding Heart
Carmellia
Carnation
Carolinia Jasmine
Castor Beans
Christmas Beans
China Berry
Clementis
Coffee Tree Plant
Cyclamen
Daphne
Delphinium
Easter Lily
Elderberry
Flax
Four-o-clocks
Geranium
Heavenly Bamboo
Hemlock
Holly Berries
Ivy
Jerusalem cherry
Lantana
Larkspur
Licorice plant
Lily of the valley
Lobelia
Milkvetch
Monkshood
Morning glory
Mountain laurel
Narcissus
NightshadeLoeander
Pea family
Pig weed
Potato plant
Pivet
Rhododendron
String of pearls
Thorn apple
Toyon
Vinca
Wintergreen
Wisteria
Tew
Pellets
It is important to note that pellets were originally intended for creating fatter meat rabbits - they are far from an ideal food for a pet rabbit, and should only be fed in limited quantities.
Do not get the pellets with seeds and banana chips and such in it - it is a treat to the bunnies but it isn't healthy and can cause stomach problems
Pellets can go stale just like bread and become unappealing to the bunny's pallate, so store unused pellets in an air-tight container, preferable in the refrigerator.
Typically you can allow a healthy growing bunny to free-feed on pellets (he can eat as much as he wants). Healthy adult rabbits should only have about 1/4 cup of pellets per 5 pounds of bunny. If your rabbit shows any signs of stomach problems, such as runny stool, take away the pellets and feed plenty of timothy hay and contact your vet.