The NCBI BioSystem, a new pathways database (http://www.ncbi.nlm.nih.gov/biosystems/) is now public.
The database can be searched directly or accessed via links from databases such as Entrez Gene, Protein, PubChem Compound, and more.  

This free resource may be a good solution for researchers who can’t afford Ingenuity Pathways or similar products.

Ready to get started?  A quick start guide is available: http://www.ncbi.nlm.nih.gov/Structure/biosystems/docs/biosystems_how_to.html