Stolen from SDFrys has a few motherboards on clearance. YMMV on availability.
Gigabyte GA-78GM-S2H 780G AM2+ Phenom Motherboard - $20
Asus M3N78 PRO AM2+ Motherboard - $20
Gigabyte GA-MA78GPM-UD2H Motherboard - $30AR
Asus M3A78-CM AMD AM2+ Motherboard - $20
Gigabyte GA-MA790GP-UD4H Motherboard - $70AR