Good choices for brushes off the top of my head:
Sonia Kashuk: This line is exclusive to Target. Good brushes (check out the sets!),
readily available, and at a good price. They also go on sale
every couple of months or so.
Studio Basics: I've seen this line at Wal-Mart. Basic brushes that work well.
ELF [Eyes Lips Face, mentioned above]: One dollar apiece?! I'll take a baker's dozen, thanks.
I use their foundation brush for spot-concealing w/mineral
makeup every day. Their eyelash curler and synthetic
flatlining brush are good, too. Drugstore.com sells these
too, and they're also a great way to "fill out" an order
in order to reach a free-shipping minimum.
Art brushes: If you have a Michaels/Blick near you (and a coupon), definitely
check out their paintbrushes. Upon closer inspection, you'll find that
the heads of many brushes are the same as those of "traditional"
makeup brushes. Something to consider for a stay-at-home set.