I am the publicity chair for my chapter, as well as a PR major, so I hope I can help you out here... :-)
1)Make a website; it's really not that difficult and if you need help I would be glad to guide you in the right direction. You can check out the one I created for our chapter at
www.geocities.com/concorddz.
2)A catchy slogan for recruitment that says something about being new...I don't know what your sorority is but if you'll tell me I'll be glad to help!
3)Lots of sorority items for backpacks, messenger bags, etc...you know, pins that have your letters on them
4)Most importantly, your members are your best PR--all slogans, t-shirts, lavaliers, etc. are your advertising. Make sure your members talk positively and enthusiastically about your organization to potential members AND anyone who asks them about it.
5)When you do philanthropy events, write up a press relase (if you don't have a comm. arts major in your chapter, your school PR person can help you do this) and make sure it gets out to local newspapers and TV stations.
I hope this helps!