Just to let you guys know, I'm still regularly adding new resources to our wiki, even if I rarely talk about it in this thread. Nevertheless, some of my recent excellent finds and additions:
Ancient Scripts - This site, man, this site !

Awesomesaucesupermegacool.
Online Conversion - Convert between units of measurement from the international system (metric system), the imperial system, customary units and many more. Offered types of measurement include lenghth, area, mass and weight, temperature. All are available in different units of measurement, past and present.
Online Calculators - Similar to the Online Conversion site. Choices offered are a scientific calculator, statistics calculator, "Exctcalc" calculator, a simple calculator, a simple calculator with an added "paper roll" results display, an RPN calculator, abacuses, simple math calculators, and a percentage calculator.