We spend far less on food without the dining plan and have more time to spend on the rides. I agree with the tip to ask for ice water at the restaurants. Its a good way to save money and stay hydrated.
When you need to sit for awhile and get out of the weather: Hall of Presidents, Carousel of Progress, Laugh Floor and the People Mover are great.
Buy ponchos at home from the dollar store. They are smaller and cheaper than the ones sold at the Disney Stores. Also bring a travel umbrella. The ones sold in the Disney store were $13-15 and fell apart after 1 use.