Various online directories. Most free, some on pay sites. Countries covered include Canada, Ireland, Thailand, UK and USA. This site is a work in progress.
http://sites.google.com/site/onlinedirectorysite
Historical local and trade directories for England and Wales covering 1766 to 1919. Note also other digitised collections to explore.
http://cdm16445.contentdm.oclc.org/cdm/landingpage/collection/p16445coll4
Find people's current addresses, phone numbers, etc. in the UK. Pay-for-use site.
http://www.192.com/people
This site has photographs and transcriptions of gravestones and war memorials in Monmouthshire and Glamorgan in South Wales. There are also some parish records, census records and trade directories. It also includes the 1873 Return of Owners of Land.
http://www.cefnpennar.com/index.htm
Transcriptions of parish registers and historical directories for some counties of England and Wales. Searchable database of death and burial information transcribed from gravestones at several South Australian cemeteries.
http://parishmouse.com