Here a few supplements that are fairly cheap you can take that definitely will increase volume and especially semen quality/consistency:
L-arginine (4,000mg/day) -- works to increase nitric oxide which helps with erection and sensitivity; also increases semen volume and quality.
L-lysine (1,000mg/day) -- increases semen quality and consistency.
Saw palmetto (standardized extract) -- I recommend a product called Prosta-Metto, sold by Puritan's Pride (
Discount Vitamins & Herbal Supplements from Puritan's Pride). This product contains the saw palmetto, pygeum, uva-ursi, and pumpkin seed oil extract, all of which work to condition and keep the prostrate healthy. If you get this product, take 4-6 twice a day with meals.
Lecithin (1 capsule/day) -- increase semen quality and consistency.
Maca -- take lots of this, as it helps increase semen volume (clinically proven to improve semen quality -- see "maca" at wikipedia.com for references).
Yohimbe -- I would recommend another Puritan's Pride product (mostly because they're the least expensive) called Viper. This product contains the yohimbe extract along with kola nut, oat straw (avena sativa), nettles, korean ginseng, horney goat weed, catuaba, muira puama, damiana, and also saw palmetto. All of these work to heighten sensitivity and pleasure during sex (which works for higher semen volumes, right?).
Amino acids -- get yourself a whey protein shake mix and drink one to two of them a day. This will help with volume. Remember, your body will use its resources for the most important things first, reproduction being towards the bottom of the list as "important." Whey protein will provide you will all the necessary amino acids, some of which work to create nitric oxide and other substances. You will notice healthier orgasms and probably increased volume.