There are many public-domain Chinese English dictionaries based on the CEDICT database. One of my favorites is included in the DimSum Chinese Tools package, but I've just come across another called Pablo that is also worthy of consideration.
Pablo has many of the features of the DimSum dictionary, with a few extra touches. Each character is shown along with a translation as well as information about its components, frequency of use, HSK level, and stroke order. Multi-character words and expressions are displayed at the top of the page, with each character being clickable to show individual character definitions.
The search function automatically switches from English to pinyin depending on the search term. Characters can be searched by radical or number of strokes by right-clicking on the search box, and there is also a writing pad for inputting characters with the mouse.
Overall, this is a very nice translating dictionary aimed at students. DimSum has many more features, but as a standalone dictionary, Pablo does quite well.
Pablo is a Microsoft Windows application, so it cannot be used on alternate platforms like Linux or PC-BSD without an emulator.