The Federation of German Industries (BDI)
Umbrella organisation. Members are 40 sector associations.
Home BDI | Member Associations BDI 

Aerospace
German Aerospace Industries Organisation

Represents all industry segments and company sizes from engineering service providers to medium-sized suppliers to international system manufacturers. 
Home BDLI | Members BDLI 

Automotive
The German Association of the Automotive Industry (VDA)

Members are divided into three manufacturer groups automobile manufacturers, automotive suppliers, and trailers, special bodies, buses.
Home VDA | Members VDA

Building Materials
Die Baustoffindustrie (BBS), only in German 
Home BBS | Members BBS  

Members lists according to material groups: 

Ceramics
Bundesverband Keramische Industrie (BVKI), only in German
Home BVKI | Members BVKI

Members lists according to ceramic product groups:

Chemicals
Association of the Chemical Industry (VCI)

Home VCI | Member Companies VCI | Member Branch Associations VCI


Construction
Verband Bauindustrie, in German only
Home | List of German Construction Companies


Consulting Engineers
Verband Beratender Ingenieure (VBI), in German only
Home VBI | Consultant Database VBI


Digital Economy
Bitkom e.V. 
Home | Members


Electric and Electronic Industry
Zentralverband Elektroinustrie (ZVEI)
Home ZVEI | List of Suppliers  


Food/Beverages
Federation of German Food and Drink Industries (BVE)
Home BVE | Member Companies BVE | Member Branch Associations BVE


Glass
Federal Association of the German Glass Industry (BV Glas)
Home BVG | Members BVG

Logistics
Logistics Alliance Germany
Home | Members | Matchmaking

Metals (non-ferrous)
Aluminium

Gesamtverband Aluminiumindustrie (GDA)
Home GDA |  Product and manufacturer database

Metals (copper, brass, bronze, nickel, tin)
Gesamtverband der Buntmetallindustrie (GDB)
Home GDB | Members Semi-finished Products and Production

Metals Foundries
Bundesverband der Deutschen Gießerei-Industrie (BDG), only in German
Home BDG | Database Foundries 

Optics 
German Industry Association for Optics, Photonics, Analytical and Medical Technologies (Spectaris)
Home Spectaris

Members lists according to product groups:


Packaging
Neue Verpackung Portal
Companies

Pharmaceuticals

Die forschenden Pharma-Unternehmen (vfa), Pharma companies doing research
Home vfa | Members vfa

Bundesverband der Pharmazeutischen Industrie (BPI), only in German
Home BPI | Members BPI

Plants/Machinery
Mechanical and Plant Engineering (VDMA)
Home VDMA | Manufacturers Database

Steel
Wirtschaftsvereinigung Stahl
Home | Members