Here are a few of the ones I remember enjoying:
Safety and Self-defense
Fashion and dressing for your body type; Colors and makeup
Host a fitness class (yoga, aerobics, kickboxing, etc)
Resume writing, getting a job, interviewing tips
Applying to Graduate School/Taking the GRE/MCAT/LSAT
Etiquette workshop
Time management, Study tips
Consequences and dangers of: Underage drinking, Using a fake ID, Drinking While Intoxicated, Public Intoxication, Aiding & Abetting a minor for underage drinking, Noise
For speakers, this site is a good resource, they manage speakers that will come to your campus to speak on a variety of topics:
http://www.campuspeak.com/
You could cosponsor with other greek groups or through the Greek Life Office.
Girls Fight Back by Erin Weed (an Alpha Phi alumna) is a great program to sponsor for your whole campus for self defense -
http://www.girlsfightback.com/