You are not only a brother for a lifetime, but also a member of the North-American Interfraternity Conference. As an alumni, you can continue your involvement in many ways. You have the opportunity to participate in your organization's alumni association, make a donation, or even become an Advisor for your organization.
Alpha Epsilon Pi: http://www.aepi.org/?page=AlumniClubs
Alpha Kappa Lambda: http://akl.org/alumni
Delta Chi: http://www.deltachi.org/alumni/index.php
Lambda Chi Alpha: https://www.lambdachi.org/alumni
Phi Gamma Delta: http://www.phigam.org/gradchapters
Phi Kappa Psi: http://www.phikappapsi.com/AlumniUpdate/Highlights/Type/PhiKappaPsi
Phi Kappa Sigma: http://www.pks.org/alumni_update.shtml
Phi Mu Alpha: http://www.sinfonia.org/alumni/
Pi Kappa Alpha: http://www.pikes.org/Alumini.aspx?mode=mpage&pid=6
Pi Lamba Phi: http://www.pilambdaphi.org/site/c.7gKKJZMzF9LUG/b.6213209/k.4CB5/Kovner_Corps_Volunteer_Process.htm
Sigma Alpha Epsilon: http://www.sae.net/Page.aspx?pid=294
Sigma Phi Epsilon: http://www.sigep.org/alumni/default.asp
Theta Chi: http://www.thetachi.org/alumni/
Triangle: http://www.trianglealumni.org/