The real Black-Eyed Susan is Rudbeckia hirta, an annual/biennial and sometimes perennial. In gardening catalogs they typically offer the small variety Todo or the Indian Summer variety with quite large flowers. Both are nice as far as they go, by that I mean they bloom for about 6 weeks and that's it so as nice as they are they are no substitute for annuals that bloom all summer. Although, if you let them go wild some will spring up any old time of the year and keep their territory colorful for much of the summer.
I started with wild ones from a wildflower seed packet and they simply pop up in place after place year after year. They start blooming in June when started early or when the plants start in the Fall. Plants that start up in spring or summer may bloom into October. Indian Summer may come back and bloom a second year. I was not happy with this variety since the flowers were so big they looked freakish and so I ripped them out the following spring, alas, I should have kept them just to see how many years they would keep going.
There is a second plant out there that is also being called a Black-Eyed Susan, Rudbeckia fulgida "Goldsturm" or orange coneflower. Normal orange coneflower has the inner parts of its petals orange but the Goldsturm plants have all yellow petals and therefore they look very nearly like a Black-Eyed Susan. The real black-eyed susan has fairly oval hairy leaves and no teeth while R. fulgida has arrow-shaped leaves with teeth. R. fulgida starts blooming in July and is a perennial and it is very commonly seen all over the place.
Later in the season there is also sweet coneflower (R. subtomentosa, once available from Thompson and Morgan) but it is much taller than either of the above. In the wild you might also find brown-eyed susan (R. triloba) with smaller flowers, its key characteristic is that the leaves have three lobes.