nciku is a free online Chinese-English and English-Chinese dictionary and language learning web site for Chinese and English, based in Beijing. The excellent dictionary features example sentences, conversations, handwriting-recognition lookup, and more, with an active community of users in the forums.http://www.nciku.com/
Free. For OS X 10.3 and above (Java). DimSum is a CEDICT-based instant-lookup text reader. Also has the ability to add romanizations to Chinese plain-text files, RTF files, and HTML pages. Includes an array of miscellaneous tools: an abacus, flashcards, Chinese name generator, GIF creator, and various converters for currency, measures, numbers, romanizations, and encodings.