Oriental poppies are really good value at this time of year, in the gap between Azaleas and most summer herbaceous colour. They can look a bit untidy, but they are much more reliable than I used to think. They come in a range of colours and are worth looking after.
A peony that we've grown for years, and has become very common is Bowl of Beauty. They stand up fairly well, but are best if planted amongst other plants which help keep them upright. This variety is always covered in colour, and both long lived and dependable.
Since I'm featuring mid June flower heads today, I thought I should include the most commonly grown Kniphofia of all. Although I've become a bit picky with pokers, and grow dozens of different sorts, there's none more reliable or easy as this one. I do have a very nice small yellow out at the moment, but its nothing like as showy as this.