Can Unity API's be called from assemblies?

I'd like to call Unity API's from an external DLL assembly I'll be making. Can this be done? For example, create a GameObject, add Components, etc.?

What would the syntax for getting that going look like? Any online samples or tutorials? (I'm more familiar with old school C++ DLL building, never done this with C#, so any help greatly appreciated).

Yeah, it's fairly simple

In monodevelop, you just right click references, click edit references, go to the last tab, then search for the UnityEngine.dll

In visual studio it'll almost be the same i'd bet (See http://msdn.microsoft.com/en-us/library/wkze6zky(VS.80).aspx )

Either way, it's not much like c++ linking, it's a hell of a lot simpler and generally "just works".

After you've done that, you'll have full unity intellisense too, yay!