You can use Visual Studio 2008 with the VS 2008 SDK targeting .NET 3.5 to create a Visual Studio Package that can run on VS 2005+. You will also need to create an installer for it.
If you don't have much need for VS 2008 support, it would be much simpler to target VS 2010+ using Visual Studio 2010 to create vsix Visual Studio Extension that is installable by itself.