Whenever I get a question like this I always begin my answer the same way: Before worrying about supplements, make sure that your training, nutritional, and recovery strategies are in place, because if they are not, no supplement on earth will be worth taking. That said, I feel the following supplements are valuable in the pursuit of increased muscle hypertrophy:
1. Protein Powders- whey protein at your post workout meal and a protein blend containing micellar casein before bed. Protein powders in general are quite useful at helping you to meet your daily protein needs of 1-2 g per lb of bodyweight.
2. Creatine- after an initial loading phase of 20-25 g for 5-7 days, take 5 grams with your post workout shake on training days, or 5 g first thing in the morning on off days.
3. Glutamine- 10-20 g per day, taken on an empty stomach, in 5 g divided doses. The best times to take glutamine are first thing in the morning, pre-workout, post-workout, and before bed.
4. Dextrose/Maltodextrin- include 50-100 g in your post workout shake.
5. Essential Fatty Acids (EFAs)- diets too low in fat will bring the output of natural testosterone to a crawl. Add 2-4 tablespoons of flax or some other EFA rich oil into your diet each day.
6. Prohormones/Prosteroids- there are many out there, but the most effective are 1-Test, 1-AD, and 4-AD. These must be taken with caution as they CAN have side effects. Also, if you are a natural bodybuilding competitor you need to know that these products may be banned for use by your federation. Follow label directions for optimal dose and usage patterns.