We have a jar on the kitchen counter with a label that says "DISNEY WORLD HERE WE COME!!!" Kids and DH put change in the jar. I hardly ever have much cash because I usually write checks when I do my shopping. So if I go to a store where I can get cash back, I always write it for $5 over. The $5 goes in the jar. If I go to two grocery stores that day, then $10 goes in the jar! Works for me since I hardly ever have much change!
So we don't have a HUGE amount of money sitting on our kitchen counter, when we reach $150 I cash it in for travelers checks. (Remember to keep receipt separate from checks in case something happens to them!) We now have $300 in travelers checks for our August trip! We also cashed in our "jar" when we bought our plane tickets and we had $103 to go towards them! It really adds up fast and our kids love counting it!
Other tips: Check out the rewards board for money earning ideas. My two favorite programs right now are Search Cactus and Netflip. Both pay cash!
Keep copies of your packing list from trip to trip. Makes it easier next time. Also when you are 3-4 months out, go over your list and make a separate list of everything you will need to buy before you go. Then each week when you do your shopping, buy one or two items from your list, like a roll of film, or batteries, etc. It helps not to have a HUGE expense right before you leave!
From one WDW addictee to another . . . have fun!!!