Water resources abstracts -
http://www.csa.com/factsheets/water-resources-set-c.php

Web of science - http://www.isiwebofknowledge.com/ 

Weldasearch - http://www.csa.com/factsheets/weldasearch-set-c.php

Well connected - http://www.publicintegrity.org/telecom/

Wharton Research Data Services - http://wrds.wharton.upenn.edu/

Who's who in American art -
http://www.marquiswhoswho.com/products/AAprodinfo.asp

Who's who in American science - http://www.marquiswhoswho.com/

Who's who in American history -
http://www.marquiswhoswho.com/products/ontheweb_history.asp 

Who's who in American politics -
http://www.marquiswhoswho.com/news/press_release07.asp

Who's who in the World - http://www.marquiswhoswho.com/

Wildlife and ecology studies worldwide -
http://www.nisc.com/factsheets/qww.asp

World database on protected areas - http://www.unep-wcmc.org/wdpa/

World development indicators - http://web.worldbank.org/WBSITE/EXTERNAL/
DATASTATISTICS/0,,menuPK:232599~pagePK:64133170~piPK:64133498~
theSitePK:239419,00.html 

World ocean database, 2001 - http://webharvest.gov/peth04/20041017175922/
www.nodc.noaa.gov/OC5/WOD01/pr_wod01.html 

World textiles - http://www.ovid.com/site/catalog/DataBase/199.jsp

WorldCat - http://www.oclc.org/worldcat/

Worldwide political science abstracts -
http://www.csa.com/factsheets/polsci-set-c.php

WormBase - http://www.wormbase.org/

X, Y, Z

Zoological record - http://scientific.thomson.com/products/zr/