Hostas, philodendron (may be poisonous to pets), and ferns are some of my favorites.
If they are too small, Yaupon holly, native persimmon, and red bud are understory trees. They can/will get large. Drawf yaupons may be an option, but they are a little bland and don'tproduce berries.
Make sure you consider the pet issue. My boxer came within a hair's breath of death from eating Sago Palm seeds.
I've had pretty good luck with the dwarf holly plants. They seem to grow in just about any conditions and require virtually no care. If you'd like a ground cover, Asian jasmine grows pretty well in the shade, too...
If you don't have too much traffic in the area, one of my faves is Leatherleaf Mahonia. LM has blue-green berries in early spring that look like grapes.
Another choice that offers color is Texas Betony. Very low maintenance and well adapted to Austin.
My favorite resource for plants is free from the city of Austin: Grow Green
All the trees I offered are native. The dwarf yaupon is a hybrid or sport of a native.
Some ferns are native.
If you have acidic East Texas soil I would recommend palmetto, curly leaf dogwood (also grows around Austin). Honeysickle will do fine in partial shade.
Hostas may originally be from Asia, but they are easy to grow and they are beautiful plants that send up flower stalks, come back every year and can be divided and shared with friends.
Can't do trees== the holes are about 3x6 and 3x10, the big obe already has a overgrown bush/tree thing in it, abd both are right up against the roof and surrounded by concrete. I'm thinking more along the lines of ground cover or bushy flowering plants that stay green in the winter. I went to home depot and couldn't find anything that was mentioned-- but that may be because I went to home depot.
Try Red Barn on Pond Springs road. They have a large selection of shade perrenials, ground cover, etc. Sounds like you would like Heavenly Bamboo, good texture, and you can cut it low without it looking too weird.
Nandinas are part of the non-native scourge, though. Their pretty red berries get eaten by birds, travel to greenbelts, and end up out-competing natives. Pretty soon you've got a forest full of nandina, ligustrum, etc. There are a few varieties that don't produce berries - but generally those don't seem to be as colorful.