Thanks for writing. Most annuals (petunias, angelonia, heliotrope, salvia, ageratum, cosmos, begonias, annual phlox, etc.) should continue to bloom well into late summer if you keep them watered and fertilized. Some, like many varieties of petunias, benefit from being pinched back to keep flushing out lots of healthy new growth and blooms.
See a great selection of annuals in our Plant Guide! http://www.bhg.com/gardening/plant-dictionary/annual/
---Justin, Senior Garden Editor, BHG.com