Speedlight for nikon d3100? - 1

I'm looking for a speedlight. The think is i'm looking for a cheaper than yn-565. I think id like to buy a fully auto mode- ttl. Any suggests?

The speedlight I bought for my Nikon D90 was the Digital Concepts 918AF.
http://www.amazon.com/...001GUZBZ2/

SB-900 AF Speedlight

The SB-900 i-TTL Speedlight leads the Nikon Creative Lighting System delivering the portability, power and versatility to support any photographer's creative lighting imagination.