I (obviously) don't know much about Unity. Can you tell me if the .unity3d file type is the equivalent of a Flash .swf file, meaning is it the compiled project? If so, what it is the source file type? Can I edit a .unity3d file? Thanks
There isn't a source file type; Unity projects are folders that contain many files. You can't edit a .unity3d file. (Aside from hacking it with a hex editor, but I'm sure that's not what you mean.)
That is a compiled web player file.
urbinsissy, You can find the answer to your last comment in this question: http://answers.unity3d.com/questions/1351/how-to-encrypt-asset-bundles. Basically, no, it's close to impossible to see what assets are in a .unity3d file.