Chalkidiki Tourist Information
The beaches of Chalkidiki/Halkidiki start just outside Thessaloniki to the south and continue all the way to Mount Athos.
Some basic information: http://www.halkidikiguide.gr/site/index.php?lang=en
WikiTravel: http://wikitravel.org/en/Chalkidiki
A nice guide from Thessaloniki to Chalkidiki - in German: http://www.michael-mueller-verlag.de/xtras/pdf/chalkidiki_leseprobe_1.pdf