Theres a hand signal that we do. Basically, its an Alpha sign. Your thumb and pinky finger are extended, the others are curled in.
It has a secret meaning that is undisclosed to the public. The meaning is only disclosed to the members of the frat. Minority college students can readily identify the sign with the Alpha Phi Alpha Organization. I learned it from older frat members. Its a nationwide signal. Its usually readily identifiable by black Greeks (black frat and sorority members). When posing for pictures, or trying to flag someone down on a college campus, we do it. Its also meant to identify yourself as Alpha, its a privilege that you earn through pledging. I was happy to finally be able to do it.
The hand signals that African-American fraternities, and sororities do are very special to them. Each of the Divine Nine (the 9 major African-American fraternities/sororities) has their own hand signal. These are displayed mostly when they get together, and on a regular basis as a greeting. I agree with Jeremiah that the sign is easily identifiable, as are those of the other groups. I think that its good that they have something that identifies them as part of an organization that they worked very hard to be a part of. It should be noted as well that anyone who is not a member of the black Greek community, and mimics their hand signals, is asking for trouble. That is horribly taboo in the black Greek community.