Munchkin Nursery and Gardens specializes in solving the question of what to plant in shady spots whether you need something for around a single tree or want to build a bed of plants from the groundcover up.
They have an email newsletter you can sign up for, a blog called "Shade Solutions", and, of course, a catalog to shop.
Here's the website link http://www.munchkinnursery.com.
You can browse through the plants, use their online comparison chart to make purchasing decisions, and even enter your price point into the system to find things you can afford.
Just to see how that price thingy worked, I entered price $5 to $10 and it showed one plant I could purchase for $10 - Virginia Bluebells. When I did an item browse though there were several $10 plants so maybe that feature has not been perfected yet.
On the left side of Shop Online there is a link, "Plants and Prices: Prices Short List" that you can click to download
There are lots of $10 plants on that list that would improve my shade beds and probably yours, too.
I like their shipping policy: $12 minimum per order plus $1.25 per plant.
The Munchkin introduction page -
Munchkin Shade Gardens are located on the north side of a Southern Indiana rolling hill. The gardens began coming to life around the early 1980’s. Soil is heavy clay over limestone with pH neutral to slightly acidic. Over the years soil had been amended or raised beds created to accommodate plants with special needs. Gene is, deep down, a collector of plants, but tries not to let the overall garden design appear as collections. Native plants are usually first choice, and curiosity is the guide once native are in place. If there are non-native relative they will eventually become a part of the garden. In the words of Dallas Foster the designer, the shade garden could be called an “exuberant wild garden”.
Check it out, especially that blog link - there's always something to learn.