Making an extension for multiple versions of Visual Studio

I have a feeling that the Visual Studio SDK is targeted heavily towards the version of Visual Studio it is created for, so I'm wondering how to do this in the best way possible. I currently only have Visual Studio 2008, but people using Visual Studio 2010 have begun wanting to use my tool as well, and I want to help them out. There were some using Visual Studio 2005 as well. Is there any way to do this without maintaining two (or three) different versions of the tool in different versions o开发者_如何学Cf Visual Studio?

This question is related, maybe it helps: Does Visual Studio 2010 have backward compatibility with visual studio 2008's addins?