Taxon on Aug 28, 2007August 28th, 2007, 11:30 am EDT
If I were to hazard a guess, it would be that the 1st and 3rd photos might be of family Aeshnidae, and that the 2nd and 4th photos might be of family Libellulidae. Both families are most commonly collected along the edges of lakes and ponds. However, identifying dragonfly nymphs is much more difficult if photographed out of the water, and even more so, if they have not reached full maturity.
Hopefully, someone here will be more experienced identifying dragonflies, and can give you more than my admittedly lame guesses.