I have a question I created on stackoverflow.com which was migrated to superuser.com, the question was answered on superuser.com but still remains in my questions tab in SO, how do I remove/hide these?
I've now created this as a Feature request.
Migrated questions remain yours on the original site until they are deleted. The question becomes a place-holder for Google Searches and for duplicate question closures. It is still a question asked by you and therefore it is not disassociated from your account.
These migrations stubs will be automatically removed after 30 days, but as mentioned by Jeff you can also flag it for moderator attention and it will be deleted.
You can flag the question for moderator attention if you really want it deleted, and a moderator can do it for you.