Learning Chinese? Reading Chinese websites? Copyfish and these free Chrome browser extensions can help you:

Zhongwen Chinese Popup Translator

Zhongwen is an extension for the Google Chrome browser that allows you to translate Chinese words by hovering over them with the mouse.

The most popular Chinese popup dictionary for Chrome. 60,000 active users worldwide. Quick, easy and simple to use. Includes useful tools for learners of Mandarin Chinese.

As a learning aid it uses different colors for displaying the Pinyin syllables, depending on the tone of the Chinese character.

How to use it: Once activated, you only need to highlight some Chinese characters and the translator, well, translates the characters to the Chinese. A must-have if you read Chinese-language websites.

Perapera

Perapera is an extension for the Google Chrome browser that allows you to translate Chinese words by hovering over them with the mouse.

That sounds not only like the tool above, it also looks like it. Both tools do the same and work well. That said, the user interface of Perapera works somewhat better for me, even though it is the less popular one of these two Chinese dictionary tools.

新同文堂 New Tong Wen Tang

You can convert simplified characters to traditional in Google Chrome with this extension, or, more technically speaking, it used used for switching character sets. The screenshots says it all:

The tool is open-source, but I am not sure under what license.

Google Input Tools

This language input tool is not Chinese language specific, but it comes in handy if you want to enter Chinese characters into a web form or web app (e. g. Gmail) and there is no built-in Chinese input method in your operating system.

As for all input method tools, the main target audience here are native speakers.