As this is a sticky, I wanted to recommend a great little book:

Greenfoods for Rabbits & Cavies by F.R. Bell now in its 9th edition.
It can be ordered from the Fur & Feather website:
Fur and Feather - General Small Livestock Titles

And a lovely poem I remember reading years ago - just looked for it online and only found one website with it on, so it does need repeating!

Feeding Ode for Rabbits
By G. Lodham
Do not give a Rabbit yew,
Spurge, Fool’s Parsley, feverfew.
Nightshade, purple flowered or white,
Lords and Ladies, Aconite.
Bryony with berries Red,
Pimpernels should not be fed.
Add Laburnum, Golden rain,
Hemlock with its Crimson stain.
Buttercup and celandine,
Foxglove, poppy and woodbine.
If they eat these, rabbits die,
Caution says 'Don’t let them try'.

__________________
‎