I have tried Avena Sativa, which comes in a tablet form, not for boosting libido, but for boosting testosterone when at the gym and in my workout plan.  I would definitely say it is one of the few things which has helped improve this and I also think it helps my general well being.

Also essential is that you are not lacking any vitamins or minerals so always make sure you are supplementing with a vitamin designed for males.

Zinc is also essential for males so make sure you have enough of this.

Hope this helps!