The Coda links - such as they are - can be found at www.decipher.com; after reaching the site, just click on the Star Trek RPG link in the top bar and it'll take you straight there.
The differences between the two systems has been examined in detail in a number of previous threads - probably the best thing to do is click on the "Search" button in the top right corner of your screen and specify "Coda and Icon differences" in the keyword bar.
I looked through the official site. I didn't find any links. Well, at least, links to additional material, like new races, and such. I didn't even see Errata....
As I mentioned before re Coda links: "...such as they are." Aside from this site, there really isn't anything out there in terms of "official" material, and fan-based DecipherTrek sites are, to the best of my knowledge, pretty much nonexistant. With the apparently imminent demise of DecTrek - and their RPG division as a whole, it seems - the field is wide open for anyone who wants to start up a support site with races and any other material you indicated.
With regard to errata, it's pretty much limited to the Coda System and Mechanics forum stickies/threads, and as I was told when I was going through an IT program about four years ago: WYSIWYG. What You See Is What You Get. There ain't no more.