Perennials for Hot Summers

My garden is looking just lovely!  Thank you all  (Or I guess I should say y'all) for your help!  I decided to sacrifice some blooms on my azaleas next summer to cut them down to a more managable size this year. 

I have reached yet another quandry in my first season as a southern gardener.  Most of my annuals like petunias and verbena that I planted back in late April are looking pretty ragged.  The verbena is covered with mildew.  (Well, what is left of the verbena--each plant has about three leaves!)  I am wondering, should I let these plants hang in there and tough it out, or should I yank them up and plant new ones?  I would like to enjoy my garden and my comfy garden swing, but looking at my half-dead plants is depressing me.

 So, garden gurus, how about some plants that I can plant now that will be able to tough it out for the rest of the summer?  Thanks in advance!

--Mary