There are many different species and cultivars of hellebores. It gets really confusing trying to make sense of it all! Helleborus orientalis (which may actually all be hybrids and more accurately referred to as H. hybridus) is fairly common in local nurseries. These are the ones that the term Lenten rose describes. They traditionally had downward facing flowers. These can grow well in containers providing the soil has excellent drainage and the container provides a good amount of root space (at least 18" deep). Several of the H x hybridus lines have outward facing flowers that many prefer. Plants from the Helleborus Gold Collection (HGC) Ice N' Roses series (coming in white, pinks, picotee and a variety of shades of deep red) have been bred for outward facing flowers. This is a series bred in Germany by Josef Heuger. The Frostkiss series also have outward facing flowers and many have beautiful variegated leaves. They have girl names: Frostkiss Penny's Pink, Frostkiss Anna's Red, Glenda's Gloss, Pippa's Purple, etc.
If outward facing flowers aren't a priority for you (I LOVE the beautiful colors of the back petals on the nodding heads of hellebores), the winter jewels series bred by the NorthWest Garden Nursery in Portland have a huge variety of colors.
Another lovely series of hellebore that doesn't have outward facing flowers are the Honeymoon and Wedding Party series from a hybridizer at Walter's Gardens. The Honeymoon series has a single row of petals and the wedding party series are doubles. I've found that the singles do better in my warm climate garden.
One down side to some of the hybrid plants is that they are sterile so you won't get little hellebore seedlings growing around them.
I've had good luck growing 'Ivory Prince" which has creamy flowers that age to chartreuse with pink streaks (stunning!) which has different parentage, it's Helleborus x nigersmithii (which I believe suggests H. orientalis/hybridus and nigersmithii as parents. It is sterile.
Helleborus argutifolius is the Corsican hellebore. I was excited to try this Mediterranean species, hoping it would do well in our mediterranean climate. Happily, it does! This hellebore is quite different in appearance from the previously mentioned varieties. It has a tall stem with cauline leaves (emerging from a tall stem) where most hellebores have basal leaves that all come out from one growing point just above the ground. These have soft green flowers. Much more subtle than many of the hellebores but beautiful in their own right.
This is only a few of the species available. If you live in a cooler climate and would like to know more, I HIGHLY recommend Pine Knot Nursery site for plants, information and for resources.
Digging Dog Nursery and Bluestone Perennials are great sources for plants.