This is a link of different SAP that can be used as a reference when digging out for knowledge, training or solutions.
SAP Service Marketplace
Catalogue to all SAP products and links to other official SAP sites.
http://service.sap.com
SAP Help Portal
SAP Documentation.
http://help.sap.com
SAP Community Network (SCN)
Forum with thousand of questions and answers from SAP users and developers.
http://scn.sap.com
SAP Training & Certification Shop
SAP Official Training Courses and Certificates
http://training.sap.com
openSAP
Free courses of the most recent SAP products.
http://open.sap.com