According to Carter, Lavranos, Newton and Walker (Aloes the definitive guide) the Aloes can be devided in 10 groups:

A. Grass aloes
B. Maculate aloes
C. Stemless aloes (in small clumps, flower stems few-branched)
D. Stemless aloes (in small clumps, flower stems multi-branched)
E. Stemless aloes (in large clumps, flower stems few-branched)
F. Stemless aloes (in large clumps, flower stems multi-branched)
G. Pendulous or sprawling aloes
H. Shrubby aloes (flower stems few-branched)
I. Shrubby aloes (flower stems multi-branched)
J. Tree aloes