Snapword is an extension for the Firefox browser that translates English words or phrases into Russian. Snapword allows to highlight a word or a phrase on any page, right click and select "Look up". List of translations is presented in a popup window on the same page. Translations are conveniently grouped by parts of speech and/or homographs. See this screenshot for an example.
All translations are provided by the on-line dictionary Multitran, courtesy of the Multitran's creator Andrey Pominov. See this page for some information on Multitran capabilities, you may also want to consider purchasing a commercial version of Multitran that provides many extra features relative to multitran.ru Web site.
Currently, only English to Russian translation is supported. There are plans to add support for more languages and other dictionaries (which should be straightforward given the fact that internally Snapword uses industry-standard TEI XML encoding as the protocol for interfacing with dictionary providers).
To install Snapword, click on this link. You may see a message at the top of the page: "To protect your computer, Firefox is preventing this site from installing software". Click on "Edit Options..." button available in the upper right of the screen, then on "Allow" and "Close". Now click on the installation link again. Click on "Install Now". You will need to restart Firefox to complete the installation (note that this requires closing all open Firefox windows).
You can also download the Snapword installer using the link below and then run the installation by opening the file using "File"/"Open File" menu item.
Note that Snapword has only been tested with Firefox 1.5.