US Patent & Trademark Office
  Home Page: http://www.uspto.gov/
  Patent Search:  http://www.uspto.gov/patft/index.html

European Patent Office**
  Home Page: http://www.european-patent-office.org/index.en.php
  Portal - espacenet: http://www.espacenet.com/
  Numeric, Quick and Advanced searches: http://ep.espacenet.com/

Canadian Patent Office
  Home page and Links to searching: http://patents.ic.gc.ca/cipo/cpd/en/introduction.html
  You will find the Number Search and Advanced Search links here.

German Patent Office ** 
  Patent Search:  http://depatisnet.dpma.de/DepatisNet/...

Japanese Patent Office
  Home page: http://www.jpo.go.jp/
  Advanced Search: http://www.deux.jpo.go.jp/cgi/search.cgi?lang=en
  Industrial Property Digital Library: http://www.ipdl.inpit.go.jp/homepg_e.ipdl

Korean Patent Office ++ 
  Patent Search: http://eng.kipris.or.kr/

Australian Patent Office 
  Quick Patent Search : http://apa.hpa.com.au:8080/ipapa/qsearch
  Advanced Search : http://apa.hpa.com.au:8080/ipapa/asearch

Gov't of India IP Informatics **
  Home Page/Patent Search: http://patinfo.nic.in/
 (search link in center of page)

NOTES:
1) Even though some of the patent authorities listed above have slightly different names (not actually called a "Patent office," per say) we call them that for simplicity of page layout and ease of use on this page, only.
2) The links should take you to the English versions of the web sites. If not, or you find a link that has become "stale," please drop a quick note to Support(at)IPDataCorp.com (we would appreciate it!)