Get outside the box when thinking about what your community needs. Use your ever increasing sphere of influence, be it the internet or local townspeople, to make things happen. Get friends and family involved. People can donate time, or money or creative ideas. Any help is a good thing.
If you want to host a fundraiser for a specific cause, even, and especially if, it is an international issue rather than a local one, align with an official nonprofit. They will help you in a legal sense, as well as facilitate funds raised. Though, be sure the nonprofit you choose is completely transparent in their use of funds: request an annual report.
Seek the involvement of local businesses. Often, they can donate food, t-shirt printing, sound equipment or the like for an event you may want to have. Even if they won't donate completely free, they may have discounts. The nonprofits you align with can possibly help these businesses with tax credits.
Let the local media know what you are up to. They will shine the light on your issue.
Finally, use your creative talents! If you like talking to people, talk until others get involved. If you are good at math, offer to help an effort in terms of bookkeeping. If you are good at art, lend your services to an awareness campaign. If you make videos, document an issue. If you take pictures, snap away. If you write, don't put the pen down until things improve. Blogging and setting up web sites is also a smart way to reach the world with your message.
No matter what you do, do what you love, and use the gifts you were given. That is how you change the world.