As well as what the guys have suggested, you may want to also try some Reflexology treatments. A non invasive way of stimulating the organs responsible for the production of Testosterone, and a great way of relaxing.
The best way to do this is to do low reps high weights. Aim for 4 - 6 reps of 80 - 90% of your 1RM. Your muslces and body will adapt to this increase of intensity, increasing your testosterone levels