Maybe others will have some good links for you... but as far as hydrangeas go:

Bigleaf mopheads: Do not prune Fall/Winter. You'll cut off next year's blooms. As a general rule, these shouldn't be pruned after mid-July (of course they are blooming then... so the best bet is to leave them be if you can.)

Endless Summer/Forever and Ever etc. (reblooming types) you can bloom whenever: Fall or Spring since they bloom on new wood

Limelight and paniculata types: Can be pruned in the Fall or Spring---whenever--they also bloom on new wood.

Annabelle (arborescence types) can be pruned in the Fall --they bloom on new wood

So before you begin---first make sure you know what type of hydrangea you have, and then go from there :)

I got the impression you were looking for general purpose resources, not only hydrangeas. If that is the case, you can review some of these books (they are not online but you may find them useful): American Horticultural Society Pruning & Training by Christopher Brickell and An Illustrated Guide to Pruning by Edward Gilman. The online websites that I have seen tend to be limited to a specific plant or tree such as this one for hydrangeas: http://www.hydrangeashydrangeas.com/pruning.html

and this one for rhododendrons: http://www.rhododendron.org/v47n2p79.htm

University websites contain a lot of pruning, care and pest control information, especially for plants grown in the university's own state.

Thanks.
Re endless summer hydrangea, So they can be pruned at anytime of the year, but where exactly do you cut them? Just cut the head bloom off or further down? thanks

In the spring, after some initial growth appears, I prune out anything that is brown and obviously dead. As for the brown blooms, you can clip them off any time you wish. Other than that, I don't do any other pruning, but I do have a couple new paniculata hydrangeas--Vanilla Strawberry and Pinky Winky--I may trim them back by about 1/3 next spring, just so they won't get too tall. But I'll have to wait until spring to make a decision on that. Quite possibly I may treat them the same as my other hydrangeas.

Hope that helps.

Kate