Answers.com gives a pretty good but very basic description of the major US gangs. However, there are so many subgroups and variations that you can't completely cover everything about them. Changes happen all the time and keep the police officers who monitor the gangs busy full time. Just for example, NYC has something like 100 organized gangs, some of which are affiliates of the Bloods or Crips and others that are not. Each group has its own distinct traits and gestures which might look like those of rival gangs but carry different meaning. There are entire college courses and professional courses that cover this type of stuff and even the best of those are often topical at best.
"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."