Recruit, recruit, recruit!
Talk to your friends, family, coworkers, classmates. Anyone who you can think of that will listen. Even if only two people from each group join, that's still 8 more people in your organization than before, and that's 8 more people with ideas for fundraising. Also, don't be afraid to tap the resources of other organizations, even ones you aren't involved in. Go to meetings of other organizations and speak briefly about yours. Maybe a few will decide to join.
Be sure to hold events to get your name out there. Have a table at activity fairs, expos, conventions, whatever there may be in your town or school. That way you are able to talk to people who are already open to looking for new organizations to join and participate in.
Take advantage of Listservs. Different universities and colleges have different regulations, so contact listserv administrators to find out what the rules are. But send out mass emails. Most people probably won't read your email, but there are always some people who do, and those people may be the ones who decide to come out to your next meeting. Listservs can be in all different varieties--classes, other clubs and organizations, offices on campus, departments, athletics, or even the entire university or college. Use these listservs to your advantage and send out an information filled, but brief email. If your email is too long, no one will read it. Make it short, sweet and to the point with all the important and relevant information about meeting times and places.
When you attend events to get your name out there, make sure that your purpose is clear. Have posters, photos, a slideshow on a laptop, and people who understand the mission of your organization there to answer questions. Set up a table during a high traffic time in a main building on campus. Cosponsor events with other organizations. Get noticed!
Be heard! Get out and talk about your organization. Give speeches, talk in front of your class briefly before it starts if your professor allows you to, network with other groups who have similar goals or topics. All of these are great ways to expand your membership.
Hold interest meetings! I stressed this is my post yesterday, but they are really important! People who want to join might feel funny coming out for a regular meeting without really knowing what you're all about, so interest meetings are a safe way to allow people to hear your spiel.
Don't forget to have fun! If you are fun, happy and welcoming people will feel more comfortable approaching you and getting involved! Have socials, movie nights, potluck dinners, etc. These create a relaxed atmosphere where people can get involved while having some fun with food or a movie.