A quick overview:
For Steelwork consider:
Graitec Advance Steel (already mentioned)
Tekla Structures.
Strucad.
MultiSteel.
ProSteel (already mentioned).
For Building Services consider:
CadDuct.
For Process Piping consider;
AutoPlant.
Cadworx.
Plant 4d.
Autocad Plant 3D.
For Architectural consider:Autocad Architecture.
Revit.
For P&ID:
Autocad P&ID.
Using the right combination of products can provide the additional benefit of direct share of 3d model data with manufacturing, thus reducing the production of 2d drawing deliverables to convey design intent.