++++++++++++++++++++++++++++++++++++++++++++++++++++
Domestic US callsign servers, contain some non-USA calls:

Buckmaster's
http://www.buck.com/cgi-bin/do_hamcall

QRZ
http://www.qrz.com

U of AK
http://www.ualr.edu/~hamradio/callsign.html
This server from the University of Arkansas is fast, and up to date

++++++++++++++++++++++++++++++++++++++++++++++++++++
Andorra
http://www.sta.ad/ura/qsl.htm
I wish I had opportunity to use this one

Belgium
http://www.as400.realsoftware.be/Org/HAMRadio/Callbook/CallRequest.htm

Bermuda
http://www.bermuda-shorts.com/rsb/callsign.htm

Canada
http://www.rac.ca/callbook/    
Most Canadian calls are in QRZ and Buckmaster

Croatia
http://www.hrs.agram.com/callbook/index.cgi

Czech Republic
http://hippo.feld.cvut.cz/cgi-bin/getaddr

Estonia
http://www.estpak.ee/~andrew/ham/es_callbook.htm

Finland
http://hes.iki.fi/oh/

Guernsey
http://www.guernsey.net/~sgibbs/amateur_radio/gu_calls.html

Iceland
http://www.guernsey.net/~sgibbs/amateur_radio/gu_calls.html

Italy
http://www.nikos.com/home/nonprof/callbook/

South Africa
http://www.sarl.org.za/callbook.htm

Tajikistan
http://www.geocities.com/CapeCanaveral/Hangar/5873/callbook.html
ASCII list, be patient, loads slow.


OTHER TOOLS:

QSL Managers
http://qsl.425dxn.org/
QSL INFO SYSTEM by IK4LZH

LOOKUP:
This is an email callsign server which seems to contain a smattering of
calls from around the world. It gave some acurate info for calls I know,
and comprehensive returns for some calls, including email addresses. 
Send a message to:      lookup@qrz.com 
In the message body: 
        lookup callsign1
        lookup callsign2
        lookup callsign3
        ...
This server is maintained by Fred Lloyd (AA7BQ) <flloyd@qrz.com>. 


There's also turkish online callbook
http://trac.eu.org/call.html