Chinese Dictionaries
Skritter is great for learning characters and words, but you're still going to need to look things up. Here are some of the best online Chinese dictionaries.
Hanping Chinese Dictionary is your friend if you want a Chinese dictionary on your Android that supports Skritter. We've worked with the developer of this dictionary to enable users to simply click characters or words and study them on the Skritter Scratchpad in one fell swoop!
The MDBG Chinese-English dictionary is the best dictionary we've found. It's got handwriting lookup, sentence lookup, translation, quick searching without having to specify whether you're putting in English, pinyin, or simplified or traditional Chinese. It's based on the free, open-source CC-CEDICT dictionary, which we love and use in Skritter.
nciku is a large, free site for gathering dictionary definitions and example sentences, managing vocabulary, and testing yourself on words and characters. They have some good word-based pronunciations, which is quite useful. Like MDBG, it has handwriting lookup. With its example sentences, it makes a great reference tool.
PlecoDict is a mobile dictionary that has some of the best character recognition out there. It has a bunch of powerful add-ons that can get spendy, but are very worthwhile for serious learners. They have apps for iPhone, Palm, and Windows Mobile.
The Taiwanese MOE is a great resourcefor checking the stroke order of traditional characters. We use it as a reference every time someone asks us to correct traditional stroke orders and is particularly handy for variants.
Wenlin, is a powerful dictionary based on John DeFrancis' ABC dictionary. It's incredibly thorough and especially good for sussing out which definition is accurate. We use it here at Skritter to double check definitions. The interface looks like it was designed in 1995, its flashcards aren't great, and it's not web accessible, but it does what it's was intended to do: rock Chinese lookup hard.
Dict.cn has example sentences in Chinese and English for words that you look up, which is useful.
Mandarin Tools has a well-done Chinese to English dictionary based on CEDICT and a plethora of tools for learners.