Seeds are very high in fatty oils and are usually only eaten by wintering animals. As a result, seeds should be fed very rarely. Do not feed at all if your rabbit is overweight.
As per my vet says:
Be warned that Rabbits are more sensitive to fat than humans, and in addition to obesity, the excess fat can accumulate in your rabbit’s liver and arteries (atherosclerosis). Veterinarians have reported that rabbits fed seed-rich diets have a much higher incidence of fatty liver disease (hepatic steatosis), which is often fatal. Acute episodes of GI stasis and dysbiosis are common following ingestion of a large volume of seeds.
If you decide to feed seeds, the following types of seeds are safe.
Flax (linseed)
Melon (e.g. watermelon, cantaloupe, honeydew)
Pumpkin
Safflower
Sunflower
Squash
Make sure that these seeds are unsalted. Feed no more than one or two seeds per 4 lbs of rabbit a day to prevent weight gain. Make sure that the seeds are part of a balanced diet with plenty of hay and veggies. You may wish to hull the seeds since the shell is indigestible, but the hulls also provide lots of fiber for a rabbit.
Here is the result of a seed feeding rabbit and the sad story
http://www.rabbitsonline.net/showthread.php?t=27306