Ugh. I'd go see the allergist and maybe get a referral to a gastroenterologist. It could be allergies, intolerances, food aversion, FPIES, EE, EGID... some of those are best treated as early as possible.
I know a great allergy group on Yahoo if you need information/support. http://health.groups.yahoo.com/group/TerrificKidsWFA/ There are 700+ members in this group, so it's a great resource for finding people who have been through what you're going through.
If he's literally vomiting after every food I'd wait to introduce anything else (I know, obvious) but you might try a food with a low allergenicity to see if that helps. I've got a toddler who is intolerant to a bunch of stuff (including RICE!!) but he's been fine all along with sweet potatoes, carrots & squash. (Yeah, he's a little orange. LOL) Here's a list of allergenicity of different foods. http://www.allergynutrition.com/resources/FAQ/15/Foods%20... or here's a tiny version: http://tinyurl.com/6frugs in case the first doesn't work. If you do try foods (and he can keep any of them down) you might want to keep a food diary. Some foods can cause delayed reactions, too.
Best of luck! I know, this food thing can be a nightmare... hang in there!