There are a ton!
Check out the official web sites of each of the NPHC sororities:
Alpa Kappa Alpha:
www.aka1908.com
Delta Sigma Theta:
www.dst1913.org
Zeta Phi Beta:
www.zpb1920.org
Sigma Gamma Rho:
www.sgr1922.org
There is also a general reference book that details the history, purpose and accomplishments of the nine NPHC fraternities and sororities: "The Divine Nine". You can buy it through almost any bookseller, online or offline.