MacinCloud - MacinCloud is a Mac cloud platform that provides on-demand Mac cloud servers, flexible dev workload infrastructure and comprehensive Mac in the Cloud solutions
Padlet - Visual boards for organizing anything.
XCodeClub.com - Rent your own private Virtual Mac with latest XCode.
BookWidgets - BookWidgets is an excellent application that let you create engaging exercises in minutes and easily share a varied variety of beautiful and fun activities with your classroom and others.
VirtualMacOSX.com - vmOSX -- is your affordable, Mac-based home on the web.
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.