This article on Wikipedia lists character simplifications and is extremely useful if you already know one character set and want to learn the other. I have written about learning both character set... Read more.

en.wikipedia.org

This add-on is available for Firefox, Chrome and Safari (and allegedly all other browsers) and allows you to switch between character sets on websites. Note that the conversion is of course automat... Read more.

simplified-traditional.blogspot.tw

This is a tool that adds a pop-up dictionary to Chrome. I haven't compared it with [Pera Pera](http://resources.hackingchinese.com/s/sltbee/perapera_language_tools_popup_browser_dictionary) in deta... Read more.

chrome.google.com