At the moment the bees are busy buzzing around the perennial cornflowers (centaurea montana) in our garden. Apparently these are wildflowers, originally from the mountain regions of France and Germany, but we have always had loads of them in our garden; they spread so easily and sometimes, when the first flowers are over, they will return later with more. I think they are really pretty and encourage them. They are early blooming this year, when we first came here thirteen years ago they didn't start to flower until mid June now they appear in mid-May.
As well as attracting bees and butterflies the flower has other uses too, I've never tried it but apparently you can (as with nasturtium flowers - which I have eaten) put them into salads. You can also (see links) make tea with them and they are supposed to have soothing and astringent qualities that can be used for natural medicines. This seems to apply to both types of cornflower. What a very useful plant to have in the garden.
An added bonus is that there are so many of them that you don't feel guilty taking one or two from the bees to put indoors.