DH isn't a Disney fan, so if I want to go, I have to be the one to save the money. Fortunately, we've got good communication on money stuff, so he pays all the bills except for my student loan from his paycheck, and I just cover the student loan with my salary. He gets paid way more than I do, so it's made sense for us to do it this way. My rule is that if I pay $800 for my loan, I can put $400 in my "Disney account". If I only pay $400 on the loan, I only put $200 towards Disney. It helps DH feel better about my saving for a WDW trip, and I learn some fiscal responsibility!
By cutting back on the little things, I have more money each month to pay my student loans, and so more money can go into the Disney savings. So I make my own lattes and such at home (I've had my espresso machine for 6 years now...), I shop at Goodwill instead of Macy's, I bring lunch rather than going out, I borrow books/videos/DVDs/CDs from the library or friends rather than buying them, I use a cheaper hairstylist and limit the number of visits per year, etc. etc.
I also periodically sort through our books, clothes, etc. and sell stuff on eBay or have a garage sale. Any money I get from stuff I sell goes straight into the Disney fund - DH says it's my "pay check" for the hours I put into selling the stuff, and he likes it that we're paring down bit by bit (combining his stuff and my stuff into our 800 sq. ft home has resulted in a lot of clutter and feeling rather cramped...more stuff for me to sell on eBay!).