I have used these on-line dictionaries extensively on an as-needed basis for German and French. It is very easy to obtain a translation for a given word from the dictionary, though generally only one translation without further description is given. This makes it a good tool for someone with experience in the language who has forgotten or needs a specific piece of vocabulary. Ideal for on-line tasks, since the lookup is quick and one does not need to leave the task to look for a book.
The dictionaries are self-installing executables. After installation one simply clicks on "search" to look up words. Switching between english-foreign and foreign-english is done by clicking on the flags on the home screen. There is an "add" feature as well as a "Practice" feature for drill.