There was Viper (I am sure there is a play somewhere here with COBRA or izzit CORBA ?), Falcon, Wolfpack, COM+ (I dont think it has a codename), .NET Remoting and now Indigo, which happens to be Green at first.
Of course, the Development and Database tools were codenamed after places (Everett, Orcas, Yukon, Whidbey, ...) Incidentally, the belief was that the further the codenamed "place" was from Redmond, the later the shipping dates will be. I dont really know the accuracy of that though.
Of course, my interest has always been in the domains of distributed computing and I have been on Viper since Day 1 and moving along with each new evolution of distributed computing technology. I am deeply entrenched in Indigo today, which some people have argued it is more of a revolution of distributed systems in terms of its perception. I dont disagree. However, I always chose to believe that Information Technology should be deployed for the sake of Business Innovation and not just for the sake of technology. This hasnt happen before BUT I strongly believe it is set to change with the coming of age of technological (horizontal) and business (vertical) standards and Indigo is set to deliver that set of technological standards while enabling vertical standards to be built on top of it. Put it all together and you get real Service-Orientation which preaches to the idea that Business drives IT and not the other way around.