I have a Multibit wallet with 0.1511 BTC on it, I want to send it back to another online wallet (on Bitcoin Central) but can't because apparently, I need to have, at least, 1 BTC but I don't want to feed my wallet more so it looks like my BTC are stuck.
There definitely should be no requirement that you have at least 1BTC in order to send BTC from your Multibit wallet. Would you be either able to screenshot the error message your getting or post it word for word? Are you sure you downloaded the official Multibit client and not some virus laden one trying to scam you?