Never heard of any. Most are full board. You pay for drinks and use of facilities such as Spa.
I went on Thomson Celebration in Jan 2008 and that was all inclusive, and very good too. If you check with Thomson, I think for the med its is about £7.00 pp per night, not sure how much for the caribbewn.
You need to book early to get the best deals on the AI package as they are limited. If you're lucky you can get AI for free, but leave it too late and you could pay more than £149 depending on the duration. The AI package has to be booked before you board the ship.