The most well known of them all are the Encore Series, sold just about everywhere (HD, Lowes, etc). They were bred by crossing them with other plants that bloom in the Summer. They have three flushes in teh South (Spring, Summer and Fall) and their Spring bloomage is the heaviest of the three. As such, there is a wait time in-between flushes. Chiffon, Coral and Ruby are the smallest of the bunch. Check below for a list of all the Encore Azaleas. I have not seen any true reds in their list though. Some of those red-looking ones tend to be dark pinks instead so personally view the ones you are considering just to make sure you like the bloom color.

Red Ruffles is a non-Encore Azalea that used to rebloom almost every year on its own for me here in Texas, that is until the pooches declared war on a squirrel up a tree and broke it in half. RR does not do that everywhere (northern states for example) so geography, climate, etc may have been other factors that made it do that. Thus, take it with a grain of salt and an understanding that other Red Ruffles may not do the same. Again, the reblooming was a little on the weak side, nothing like the Spring flush. I never noticed blooms in the Summer but saw them when temperatures finally went down in the Fall.

Here is a link that might be useful: Encore Azalea List