"National Lawyers Guild Legal Observer Training Manual":
http://peopleslawresourcecenter.org/nlg/LO_Manual.pdf

"National Lawyers Guild Instructions for Legal Observers":
http://www.nlg-la.org/handbook.htm

On campaign strategy:
http://www.campaignstrategy.org

"Designing Effective Action Alerts for the Internet":
http://polaris.gseis.ucla.edu/pagre/alerts.html

On volunteer management and motivation:
(see especially the Library section, by subject)
http://www.energizeinc.com
(also see the website below, re: a formal process used for volunteer management in the US)
http://www.casanet.org/program-management/volunteer-manage/essenvol.htm

The Nonprofit Genie:
(geared towards California nonprofits, but there's a lot of good general resources in the FAQs section)
http://www.genie.org

Nonprofit Risk Management Center:
(assists nonprofits cope with uncertainty; offers consulting and resources on a range of risk management topics)
http://nonprofitrisk.org

On strategic planning:
(the third link is a free on-line strategic planner, allowing you to create and edit a three-page strategic plan)
http://nonprofit.about.com/od/nonprofitstartup/a/planning.htm
http://www.managementhelp.org/plan_dec/str_plan/str_plan.htm
http://www.planware.org/strategicplanner.htm

On facilitation, decision-making, effective meetings, power dynamics, etc.:
http://www.zhaba.cz/materials/materials.html

On fundraising:
http://www.zhaba.cz/materials/Money/Intro.html
http://www.fundraisingdirectory.com/FundResources.htm

To advertise job openings, events and volunteer opportunities:
http://www.idealist.org

"Nonprofits: Getting Your News in the News":
(on writing press releases, etc.)
http://www.saja.org/nonprofits.html

"Translationsforprogress.org":
(Free on-line database links language students interested in volunteering with overseas NGOs that don't have the budget to accommodate professional translators.)
http://www.translationsforprogress.org