I have been studying which plants attract the most bees for 6 years now and, as a family, the heleniums really do seem to be a winner. There are a lot of heleniums (around 40 species and many hundred cultivars) so we have not studied that many but I have yet to find one that is not highly attractive to bees. This is even true of those that have been 'improved' through breeding to have bigger flowers or specific petal colours. This is really good news as most of the ones sold in garden centres tend to be those that are subject the latest marketing investments but even if they are sterile, they seem to mostly still have some nectar.
The classic popular varieties include 'Sahin's early flowerer' and 'Moorheim beauty' both of which are stunning plants and attract a range of wild and honey bees.
At rosybee, we were lucky enough to stumble accross a seed supply of a variety that seems to be either the species plant or very close to it; helenium autumnale. It has smaller flowers but many more of them, the latter point probably being the reason it attracts so many bees. I find that when the flowers begin the bumblebees are attracted, then as the plant reaches full flower the honey bees decide its a worthy nectar source and decend. If you look carefully then sometimes, amongst the honey bees, we get tiny solitary lassioglossum bees.
Heleniums like full sun but are quite tolerant of soil type. They provide reliable and long-flowering late summer colour in bright hot shades. No garden should be without a clump of these stars.