The Bavarian Illuminati was real, the rest, well...Illuminati is by far one of the most used and most general words ever. Nothing distinctive about it, besides being mostly known for being used in fiction, every bored hacks little shindig of losers calls themselves the Illuminati stuff or that, glorified fondue parties. Seriously, everyone for 2 centuries has used the term in various wise.
The only conspiracy I care about, though its not much of a conspiracy, just not too much talked about reality, is that the American Military industry/complex rules the world as they see fit. Someone should have listen to dear ol Eisenhower when he said (after releasing what he has done) leash that puppy before it turns into Cerberus