Hire a company.
If fundraisers you have to plan are not your thing, there are plenty of companies out there willing to do the work for you. You buy their product at a discounted price and then sell it for a profit. You keep the difference, turn in your sales sheets and they deliver the items to you to distribute.
Team up with a local business.
Most businesses will have nights where 25% of the profits will go to your school, or will distribute fliers and if families bring them in when they dine, 25% of what that family spent will go to the school. These can generate a lot of revenue or just a little. It depends on how much you advertise for the event.
Hold a bake sale.
The simplest and oldest fundraiser known to man. Ask every parent in the class to make something to sell, like brownies, cakes etc.... The catch: in this day and age, most schools will not allow homemade food items to be distributed at school. Which makes this type of tried and true fundraiser more difficult to hold.
Modernize it: Instead of a bake sale, hold a coffee sale. Sell gourmet coffee before school to teachers and high school students or at parent/teacher conferences. Set up a "drive through" in the drop off line for parents bringing their little ones to school.
Have a Garage Sale.
Get the whole school community to contribute their old stuff and hold a huge garage sale in the school gym or parking lot. All proceeds go to the school and people get rid of their old things. It's a win/win.
Sell T-shirts and other school-spirit paraphernalia.
See a local printer and have them print t-shirts, sweatshirts, hats and more with the school's logo. Sell them at a school "spirit shop" during lunch and after school. Sell them at sporting events as well.
Tip: Order a variety of sizes. I teach at a high school and have bought spirit wear for my little ones to wear to football games, this means onesies and toddler sizes.
Order in bulk and ahead of time. Every time you "re-order" it will become more expensive for the "set up fee." Try to anticipate the amount you will sell and avoid putting the year or other material that will date the items, that way you can sell them many years in a row.
Have a variety show.
Call it variety instead of talent because everyone is talented. Hold try outs and do not accept just everyone who auditions. Be picky. Choose the best of the best and have variety. At my school, we choose acts that dance, sing, tell jokes, and perform acts from plays and more. This is the most successful fundraiser at my school. Sell tickets at a discounted price if they buy before the event and raise the price for those who buy at the door.
Hold a dance.
This event is a lot more involved, as you need to have a DJ, permission from the school, decorations and more, but it is also a HUGE money maker. Get a parent to DJ or get a good deal from a professional (maybe they can write it off on their taxes.) Get parents to make the snacks and drinks and to chaperon. Arrange with the photographer for a percentage of the picture package sales to go to the school. Everything else is just revenue. Sell tickets at affordable prices so as many students as possible will attend. Sell spirit wear at the dance and have a raffle at the dance. Every student who buys a ticket is automatically entered to win a prize, like a free sweatshirt or yearbook. Arrange with donors in advance so that you are not actually losing any money on the prizes.
Trivia Night.
Recently these have risen in popularity and they are a lot of fun to hold. Advertise your trivia night around town and couple it with a silent auction. Get donations from local vendors for the auction. If you give students incentives to sell tickets you will get a bigger turn out easier. Have it at a venue that allows alcohol (not at school) and buy one or two kegs to serve. People bring their own food to these events. Have a 50/50 raffle. The more people drink the more they are willing to spend. Start collecting for the 50/50 raffle halfway through the night and announce the winner at the end of the night. (With a 50/50 raffle the winner gets half of the proceeds from all of the tickets sold and the organization gets the other half.) Have the silent auction going all night and announce the winners at the end of the night. The winners of the trivia game get a money prize. Usually just their money back and usually they will donate it back to the cause.