World Intellectual Property Office:
http://www.wipo.int/portal/en/index.html

USPTO:
http://www.uspto.gov/

USPTO - MPEP:
http://mpep.uspto.gov/RDMS/detail/manual/MPEP/current/d0e18.xml

USPTO - PAIR:
http://portal.uspto.gov/pair/PublicPair

United Kingdom Patent Office (UKIPO):
http://www.ipo.gov.uk/

Canadian Patent Office (CIPO):
http://www.cipo.ic.gc.ca/eic/site/cipointernet-internetopic.nsf/eng/Home

Search engine - USPTO:
http://patft.uspto.gov/

Search engine - EspaceNet:
http://worldwide.espacenet.com/

Search engine - Google:
https://www.google.com/?tbm=pts

Search engine – Japanese Patent Office (JPO):
http://www19.ipdl.inpit.go.jp/PA1/cgi-bin/PA1INIT?1174893108866

Search engine – Australian Patent Office:
http://pericles.ipaustralia.gov.au/ols/auspat/welcome.do;jsessionid=TvTNTByPmMYj2r1jpnPLyxtDb9nTTdh7x29XGRGv7wv9dpXG4T0M!-1060316002

Newtone Patent Searching:
http://www.new-tone.co.il/