I think this would be too long a question to answer. The 20s may well be the age that slang caught on, radio was becoming popular, new forms of music brought new terms and young people were more important as a group - although I suspect that people have said this about every decade since the neolithic.

See http://local.aaca.org/bntc/slang/slang.htm for a list. You have to take the dating with a pinch of salt, some much older terms may have been first recorded in print in the 20s because of wider newspaper circulation or some much later terms could have been back dated to the 20s because they seemed to have a link with Jazz or prohibition.

See the question on nitty-gritty for examples of words that were apparently common in the 20s but not recorded in print until the 60s, especially terms used by groups that didn't own newspaper chains.