I LOVE LOVE LOVE
Aveda's Hang Straight it goes on like a leave in conditioner and never ever makes it stiff, if anything it is more soft after using it. BUT it totally works!
I also have a really nice (and kind of pricey) professional hair straightener that works great -- With straighteners you really do get what you pay for.
Here is the link for the product--
Aveda Hang Stright