Hostas, Rhododendrons, Azaleas grow well in the type of soil under pine trees and they don't need much sun. I use them a lot in shady areas under pine trees in my landscape jobs. Also Heuchera (Coral Bells) is another good idea. Hosta and Heuchera are perennials while the Rhoddies and Azaleas are shrubs. You can find lots of different colors and sizes and there is even an Exbury Azalea that is deciduous that is has a very pretty bloom.

There are also some sedum ground covers that would be nice as well. Some of the variegated ones do very well in shady, acidic soil.

My advice to you is to talk to your local nursery (not the box store ones) and see what they suggest for your area. One thing about Rhoddies is they prefer well drained soil so you might have to add a little sand to the planting area, but other than that, each year adding some fertilizer for those plants, they should do fine.