Adding custom menu on right click to project in solution explorer (Visual studio 2010)

I have been trying to add another option in the right click menu (just above Add references) to build some come packages.

I am using VSPackaging (VS 2010) for this. The problem is I am not able to get the correct Guid with which I can get the button in its right place.

I tried the following:

<Menu guid="guidSHLMainMenu" id="IDM_VS_CTXT_ITEMNODE" priority="0x0000" type="Context">

but this only gets as far as getting a control at an item level and not at the project level.