Easiest way to write pinyin with tones

http://learningchineseonline.net/ Here you can find an extremely useful way of writing pinyin with tone marks.

Games for practicing simple vocabulary for kids

You can find some simple online interactive games for kids to practice vocabulary here

The Periodic table

Wikipedia has a Chinese periodic table here

A Chinese crossword

Here is a Chinese crossword:

http://www.eboic.com/Func/FillWords/cross.asp

Sudoku for learning Chinese characters

You can find a Sudoku for learning Chinese characters here

Chinese Loan words in English and English loan words in Chinese

Here are 2 lists of loan words in the two languages concerned:

Chinese loan words in English

English loan words in Chinese

A game for learning to differentiate Chinese characters

Here is an activity for learning to differentiate similar characters: click here