Documentation:
Developer/API Documentation
http://developer.salesforce.com
 
General informations for nonprofits
http://salesforcefoundation.org/product
 
Nonprofit Resources Page at Salesforce.com
http://www.salesforcefoundation.org/resources
range of links, from Just Looking/Getting Started to Intermediate and Advanced topics.
 
NPSF Wiki
http://wiki.developerforce.com/index.php/NPSF
Wiki for Nonprofit Practitioners of Salesforce.
 
Roadmap for the future of the Nonprofit Starter Pack
http://code.google.com/p/npsp/wiki/RoadMap?ts=1...
Draft plan for future development of the Nonprofit Starter Pack.
 

 

 
Useful Links:

 

 
Training:
Creating On-Demand Applications with AppExchange
http://www.salesforce.com/landing/register.jsp?...
Register to download your free copy of Creating On-Demand Applications with AppExchange, and see how you can take advantage of everything the AppExchange has to offer.
 
Using the Salesforce.com API
http://www.oreillynet.com/pub/a/network/2006/11...
O'Reilly Network
 
Developer Accounts and Documentation
http://developer.salesforce.com
Complete access with multiple toolkits and much documentation to the salesforce.com API.
 
Live Demo for nonprofits
http://salesforcefoundation.org/tools
Live Demo via telephone and Goto Meeting. Usually about 30 attendees every Tuesday Morning Pacific time.