SBA: Small Business Administration
http://www.sba.gov/
"The U.S. Small Business Administration, established in 1953, provides financial, technical and management assistance to help Americans start, run, and grow their businesses."

Enterprise Development Website 
http://www.enterweb.org/
This award-winning collection of sites is produced by the Canadian International Development Agency. There is both a topical and geographical arrangement of annotated links.

Small Business Organizations
-- a linked list from Yahoo!

Entrepreneur.Com
http://www.entrepreneurmag.com/

The Entrepreneur's Reference Guide to Small Business Information
http://lcweb.loc.gov/rr/business/guide2.html
From the Library of Congress.

Small Business Ideas at Idea Cafe
http://www.ideacafe.com/
"The small business gathering place for business community"

Bplans.com
http://www.bplans.com/
Business and marketing plans.