Get A Grip Powder is the new kid on the block for grip during yoga. Sprinkle a little on your hands, rub vigorously to activate the grip and feel the difference in traction in a down dog! Focus on your asana and not your hands moving. Wash off with warm water and soap. Doesn't leave a sticky mess on your mat.
For really sweaty yoga you could also get yourself a Get A Grip mat towel that won't bunch up on your mat and keeps your hands and feet firmly in place as you practice.