This dictionary is based on the distribution file, provided by Stanislav Sinyagin. Please check out the list of mirrors (there is quite a few of them :).
The dictionary counts 76984 entries, 70298 different english words and idioms (remember that it has both english-russian and russian-english sections) and 32381 different english words.
Here is a list of online dictionaries, in the order of preference, and sorted by language.
If you would like to automate the word search, you can add the following link to your bookmarks: Russian Dictionary. After you do so you can select the text anywhere on the web page you're viewing, and click on this bookmark. You will automatically be shown all dictionary entries, containing the text you've selected. This bookmarklet works only in at least NS 4.0 or IE 4.0 browsers and will not work with page containing frames.