I'm with Tobian and IceGiant, in that I believe CODA is a very robust system. It is easily adjusted to allow for different styles of play (just look at Trek and LOTR), and writing alternate rules is a snap. I've seen a lovely Fatigue-based psionics system for Trek using LOTR's Weariness mechanic, for example, which works beautifully. Already mentioned was KillerWhale's Extended Starship Operations, better than a great many so-called "professional" publications.
For fans of ICON's more detailed skill system, I have always recommended tweaking the CODA skill system. Eliminate the +2 modifier for specialties and assign a -2 modifier for any use of a skill outside a character's listed specialties instead. This lowers overall character competence, but works very well if you prefer a grittier game while keeping the same advancement scheme. For me, ICON is far less robust and CODA starship combat rules.
“In our every deliberation, we must consider the impact of our decisions on the next seven generations.”
-- Great Law of the Iroquois Confederacy