I'll second Imperial clover. I planted a 1/2 acre plot in may and it's knee high now. Planting was as easy as following the instruction and sweating a lot.lol

It is good top quality forage that stays green all year. As mention above it is a perenial and will last upto 5 year from a single planting.

I also planted a small 900 sq ft plot of powerplant. This has really taken hold and the deer are in it a lot. It's an annual so it would have to replanted year after year but i've got as much forage in a 30' x 30' plat of powerplant as I have in a 1/2 acre of Imperial clover. They're complementing each other very nicely.

For pics see: http://forum.hunting.net/asppg/tm.asp?m=695337