Last summer even my Aloe vera plants got sunburned!!! there's not much you can do at that point. A lot of the plants used to beautify parking lots will usually take the hot and dry - verbena normally does ok, I find that they get spider mites really bad during the high humidity days.

DMDF,
All I can suggest is what does well for me,
Verbena (I have the gorgeous purple)
Lantana
Canna
Roses (all varities)
Daylillies (these are no care)
SPirea (awesome)
junipers
petunias (worth it even if they die off)
dahlias
blue flax
St Johns wart, evergreen
this is what I have noticed that did exceptionally well in the heat last summer, and also butterfly bush.
I love butterfly bush, one of my favorites, you just cut it down in the spring if you want it to stay smaller.

2010 was a bad summer for a garden with all the heat. My garden is in full sun, all day long and it took a beating. Here are my picks for the best heat survivors (links are to my personal gardening blog):

Agastache

Salvias, especially the greggii varieties, are great in drought.

Ornamental grasses
Butterfly bushes
Lantana

Cameron

Here is a link that might be useful: best performers in my garden

One of my favorite salvias is Mystic Spires. It blooms all summer.
I agree with listed plants so far but would include lavender and sedums.

You can get lots of interest between my big four: Roses, lantana, butterfly bushes and salvias if you plant many different varieties.
Don't forget crepe myrtles also.

will lantana take over a bed? How hard is it to control, and do the seed spread invasively? I have grown it only in pots.

Ms. huff- the most cold hardy one, gets pretty big by the end of the season about 4'x5'. It will come back, but it takes a while to get going in the spring. I've never seen it reseeding around, but it does set seed, so i suppose the potential is there. The other kinds don't tend to get as large as ms. huff. There's also a creeping, purple kind, and it stays low but gets to about 3-4' in diameter. I haven't noticed lantana surface rooting or anything that would make it spread beyond the original plant. It does root fine if you want to multiply your plants or take one in for the winter in case yours isn't winter hardy.

I have a unnamed lantana, could be 'Ham and Eggs' or 'Athens Rose' -- pink and yellow.

The taproots are very long and I keep finding new sprouts in the location where I removed a shrub a few years ago. The large ones (like 'Miss Huff') are difficult to dig up, so make sure you plant in a permanent place. I've not had the problem with the smaller lantana varieties.

A wonderful combination is lantana 'Miss Huff' with bronze fennel, salvia guaranitica 'Black & Blue', and a deep orange agastache-- if you like orange and deep blue together.

Another combination that I like is my 'Ham and Eggs' (pink and yellow) with a deep pink agastache and pink muhly grass. I also use salvia greggii 'Dark Dancer' with those. My largest lantana is planted along with pink butterfly bushes, too.

Cameron

I'll second Agastache. Given a little rain (or light supplemental watering) it absolutely THRIVES in the heat. Last year, Acapulco Salmon & Pink bloomed for 6 months straight!

Also, many succulents can take the heat, the upright Sedums always do well for me, but sempervivums (hen & chicks) do not. They seem to melt on hot, humid days.

Other perennials that seem happy in the heat include Nepeta (catmint and catnip), Salvia, Russian Sage, Lavender, Asclepias tuberosa (butterfly weed), and Echinacea (coneflowers).

I have a lot of perennials available, send me an email if interested in talking. I'm located in upstate SC near Westminster.