2C-I is a "research chemical", a phenethylamine first synthesized by Alexander Shulgin that has not been used as extensively as drugs like MDMA or LSD. There is an entire 2C-x series from 2C-B to 2C-T-9. A handful of them such as 2C-I, 2C-C, 2C-E and 2C-B-fly along with hallucinogens of the tryptamine chemical family are available through online chemical vendors.
Many of these substances havn't been around for much more than a decade, while they are related to controlled substances they are not specifically listed as illegal. Possession or sale of them could be prosecuted under the 1986 Federal Analogue act, however, and a couple incidents involving misuse of the chemicals led to Operation Web Tryp.
Online vendors were selling these substances from within the United States, and before July of 2004 anybody living in the states had full access to them. Now they are much harder to acquire, only available overseas. The one legit resource I had recently shut down.