SAP-EDI.com - EDI/ALE answers in plain English. - http://www.sap-edi.com/
SAP Development - Provides ABAP source code and information on SAP's technologies. - http://www.sapdevelopment.co.uk
SapPoint - Documents and screencams on topics of ABAP/4 programming - http://www.sappoint.com
SAPEdit - External ABAP/4 editor for SAP. Download, order online. - http://www.sapedit.com
CT-Software - Searchable ABAP Freeware Pool - http://www.ct-software.com/reportpool_frame.htm
The SapFaq - Email-based peer-to-peer technical support from experienced professionals. Home of the original MIT-sponsored SAP-R3-L Technical Support Forum. Free to qualified professionals. [Membership required] - http://www.SapFaq.com