I'll surely reiterate some of what the others have said, and some other things that might irritate fellow students; take my words at your own descretion.
Greek societies are only as good as the schools that recognize them. For instance, I was a cabinet officer for my school's chapter of Alpha Epsilon Delta. As a sophomore, it seemed like something that would make my application stand out. Issue? Some schools didn't even know what AED is, and applicants from AED chapters were likely submitting applications by the hundreds. In this regard, it was basically a gold star sticker that you have to define on your application for the college to understand. What I should note, however, is that AED is a
Preprofessional Health Honors Society - meaning that it not only signifies high academic achievement, but also provides the foundational understanding of health professions. In this regard, it required even more explanation to show that it was more than a society status granted by GPA.
Baccalaureate Latin honors, such as Magna Cum Laude, Summa Cum Laude, or Cum Laude, are based upon GPA and more commonly awarded at varying institutions. Whereas not every university may have such-and-such Greek society, these honors are more common, thus require less explanation.
There are others honors programs and grants. These make your profile stand out, but do they really say much to the person? One may argue that being an academian is necessary for medical school, but I followed a different approach when entering undergraduate programs. Every student can study to the point they get a 4.0. Not every student can study hard courses while completing several service projects, working jobs on the side, and being involved in campus life. Thusly, I focused on rounding my profile with volunteer work, on-campus positions, academic research, and thesis writing. I am not going to be graduating Summa Cum Laude, but I will graduate Cum Laude with some where around 500 hours of service, an honors thesis, and experience in a hospital that supports that I have come to a complete understanding of what I'm getting myself into by going to medical school.
I'm sorry to any Greeks and Latins I may have insulted by saying you're working extra hard for gold star stickers. I may have been a touch long-winded, and gone slightly off topic, but I wish someone would have shared some of what I've found out on my own when I was just entering college so I would have done more service and less honors. My friends and I often joke about having been in an honors program and an academic society, having written a thesis, and having completed research. At the end of your college career, it gives you the ability to wear a few extra ropes to hang yourself with later on
[
Edit] Also note that AmeriCorps offers student grants for completing service work; they're very easy to obtain, decent pay off, and look sharp on resumes. The program is called UCAN Serve.