A nice read on topical stamp collecting, and in particular, the US Flag Series of stamps:
http://www.state-journal.com/spectr...each-historyThe only comment in the article I would take issue with is the suggestion that in another 10 years the first day covers of the flag stamps are going to be 'valuable'. History has proven this not to be the case and there is no reason to think that will change anytime soon given the vast quantities of first day covers produced for virtually every issue.