I'm looking for ideas for what to plant beneath a large fir tree in our south facing front yard. There is about a 2 foot ring around the tree that looks really bare, then the lawn.

Your problem is quite common. There are a few groundcovers which will grow nicely in such a situation-just keep in mind that you will have to give the plants extra water and nutrients to maintain them, because the evergreen will be taking a lot out of the soil.

Some choices-
Arctostaphylos 'Vancouver Jade'
Cotoneaster dammeri-Bearberry
Pachysandra terminalis-Japanese Spurge
Hedera helix-English Ivy
Aegopodium-Goutweed
Thyme-various varieties
Ajuga-Bugleweed

I would recommend that you plant all the same plant instead of mixing them, the effect is better. Also make sure that you edge the lawn properly, or use landscape edging, so the plants don't move out into the turf.