None really…there are some repeat bloomers like Stella D’oro dayliliies that can send up a lesser second round of flowers but it is the nature of perennials to bloom for a specific 2-3 week period and then go to seed.  The trick with perennials is to have a mixture of early, mid and late season blooming varieties.  For all summer flowering, you’ll need to look to the annuals.  They only last one season but flower continuously right up until frost.   Roses are another option for continuous color all summer.