Aside from everything else, the main part of your rabbit's diet should always be hay, usually timothy hay (or alfalfa for young rabbits).
Most trusted sites (House Rabbit Society, as previously mentioned; as well as My House Rabbit) will tell you similar information about what you should be feeding your rabbit.
Regarding vegetables specifically:
A varied assortment of vegetables should be a part of your rabbit's daily diet. When choosing vegetables look for something fresh and free of pesticides. Always wash your vegetables thoroughly before feeding them to your rabbit. Feed new vegetables in small quantities until you can judge if your rabbit reacts well to them. Do not feed rabbits the leaves from houseplants as many are poisonous to rabbits. Your rabbit may enjoy some of the following vegetables:
- Bok choy
- Broccoli leaves (stems or tops can make rabbits gassy)
- Carrot tops (carrots are high in calcium and should be given sparingly)
- Collard greens
- Dandelion leaves
- Kale (sparingly)
- Lettuce - romaine or dark leaf (no iceburg lettuce and no cabbage)
- Mustard greens
Although that list is specific to that site, I would steer clear of cruciferous vegetables altogether, which includes broccoli and cauliflower, as rabbits will get bloated and are not able to pass built-up gas.
High-oxalate vegetables such as kale should also be given sparingly, as they can cause complications in a rabbit such as bladder stones which can only be corrected through expensive surgery.
Pellets and treats should also be give in moderation, and infrequently.
It would be beneficial to research what foods are okay for your rabbit to eat, by looking at some of the resources. It is not suggested practice to just give your rabbit whatever you can find in your fridge, as many vegetables and other foods can be harmful to their diet.