Well, can't resist .......
Jacksparrow's abso. spot on with lavender (bees adore it), and any daisy-type.
Bees & butts always go for herbs, some of which are quite decorative as well as tasty: rosemary and sage are both sure winners and don't mind being pruned hard.
If there's room then a buddleia shrub (my fave is a double white). Prune as hard as you can in late winter after the goldfinches have eaten the seeds and it will grow again very quickly and reward you with scented flowers which all and every insect can't resist.
Heathers (if you have acid soil) are easy and popular, and just for fun think about aquilegia (columbine) which seeds all over the garden and the colour-combinations change, and maybe foxglove.