Does anyone know where I can find a version of the farseer physics engine compiled for MonoTouch, or do most people just download a windows version from codeplex and attempt to build their own solution?
Farseer is based on Box2D.XNA, and looking in their repository, I'm seeing what looks like managed C++ (reference). I'm not familiar enough with managed C++ do know if it can be used to generate Mono-compatible .NET DLLs.
However, it looks like there's a native C# port of Box2D here. Just run it through MoMA and then try compiling it in MonoDevelop. I dunno if there's any compatibility scanner for MonoTouch, but last I read the main things you need to avoid are
Reflection.Emit and unsafe code, and it's not likely those are used in this port of Box2D.