There's really no secret to saving for your vacation. If saving is not already a part of your budget, you need to make it a priority. To afford that vacation, you need to do either make more or spend less. As a college student, you may not have too many opportunities to make more money. Your time is probably stretched thin as it is. A few moneymakers that you might consider: eBay, Half.com (for selling used textbooks), a yard sale or selling to a consignment shop. The amount of time that you invest in any of these is up to you, which makes all of them nice for anyone who has very little spare time. There are also online survey sites, mystery shopping and test drives that can pay well. If you get on a consumer panel, you may be offered $50-$100 for your opinion on new products and advertising.
On the other side of the coin, you can look for ways to spend less. Take a hard look at what you spend you money on every month. Are you buying new DVDs anytime they come out? Forget building that library right now and rent DVDs instead. Do you spend a lot of $$$ on lattés and cappucinnos at the coffee shop? Buy an inexpensive coffeemaker and brew your own take-along instead. Maybe you have a hobby that is costing you big $$$ every month? Or an obsession with shoes (you should have seen my shoe wardrobe when I was 25!, Imelda Marcos had nothing on me!). How about designer bags? The point is this, almost all of us have some type of spending that we can cut back on if we have a desire to do so.
Since your trip is about 1½ years away, you can probably get an idea of what it will cost based on this year's packages. Go to Disneworld.com and price out your vacation for the same dates in the 2006 season (2007 rates aren't available yet). This will give you a clue of what kind of savings plan you'll need for 2007. Keep in mind that the figure for the 2006 quote will undoubtedly be lower than the 2007 price...tickets and room rates go up every year. Increase that number by about 5%. Don't forget to factor in airfare, rental car and food. Then, divide that new total by the number of months that you have until the trip. That's your monthly savings goal for the next year and a half. If the number is impossibly high, you will either have to push back the vacation a few months or scale it back (offsite, fewer days, no hopping or magic plus, etc.).
Now that you have that monthly savings goal, you need to put the money in a safe place so that you don't accidentally spend it. A separate savings account, designated just for the vacation is probably a good idea. An online account, rather than one at a B&M bank will make it more difficult to access the money quickly, which will help to curb any impulse spending. They ususally have better interest rates than B&M banks as well. If you set up the account so that regular deposits are transferred from checking to savings, you may not even miss the money.
Finally, don't dismiss your change as insignificant. You can accumulate a good amount of change in a year and a half. I have a popcorn bucket from a previous visit to WDW. I just throw all my coins in there everyday. When the bucket is almost full, I take it to my bank. They have a free coin counting machine. I just deposit the final amount into my checking account and then transfer the funds immediately into my savings account. I do this about 4 times a year with the average amount falling in the $150 range. Very little effort and relatively painless. If you're the type to raid the coin jar, get one that is nearly impossible to open without destroying it.
Good luck with establishing your savings plan. Post again when you've outlined a plan. Maybe someone will have more suggestions for you.