Sharepoint Plug In For Visual Studio

The Addin you need for deving is Visual Studio 2005 Extensions for Windows Sharepoint Services.

 

http://www.microsoft.com/downloads/details.aspx?familyid=3E1DCCCD-1CCA-433A-BB4D-97B96BF7AB63&displaylang=en

 

There is also a version for 2008.

 

http://www.microsoft.com/downloads/details.aspx?familyid=7BF65B28-06E2-4E87-9BAD-086E32185E68&displaylang=en