Resources of all known biochemical pathways?
You can find biochemical pathways on KEGG pathway for example. 


  KEGG PATHWAY is a collection of manually drawn pathway maps representing our knowledge on the molecular interaction and reaction networks for:
  1. Metabolism 
      Global/overview   Carbohydrate   Energy   Lipid   Nucleotide   Amino acid   Other amino   Glycan 
      Cofactor/vitamin   Terpenoid/PK   Other secondary metabolite   Xenobiotics   Chemical structure 
  2. Genetic Information Processing 
  3. Environmental Information Processing 
  4. Cellular Processes 
  5. Organismal Systems 
  6. Human Diseases
  and also on the structure relationships (KEGG drug structure maps) in:
  7. Drug Development


To illustrate the information you can find there, here is a screenshot: 

If you click on kegg atlas, you get an atlas with all metabolic pathways. You can zoom in to great detail en click for further links.



If you click on glycolysis or oxidative phosphorylation for example, you will get linked to the following page (see picture). In these detailed schemes of the metabolic pathway, each intermediate can be clicked on, leading to a more detailed page.