Off season weight loss

Hi,
This is my first time posting on this site.. I have just completed my first tri season, I did a sprint distance, a slightly longer tri, then an Olympic distance tri about a month ago. I did okay, but now I want to make the best use of the off season by losing as much weight as I can, and also building a good aerobic base for next season....
Does anyone have any good suggestions for off season workout sessions/plans to do this so I can improve on my times for next year.
Gotta say what a great sight this is by the way, so helpful!
Paul