For those learning Chinese out there, I thought I would mention some of the most useful resources I have found for learning the language.
By far my favorite Chinese lessons. The lessons focus on spoken Chinese and are in podcast form, so they are meant to be downloaded and listened to on your computer or mp3 player. Each lesson focuses on a pre-recorded dialogue, which is listened to and then discussed and explained by the two hosts (one native English speaker and one native Chinese speaker). The lessons are divided into five levels, so they suit any level of Chinese learner, and the topics are a good mix of the practical and the interesting. I particularly like ChinesePod because the lessons are well-written and teach Chinese the way Chinese people actually speak it (I'm amazed by the number of Chinese learning materials that fail at this), the hosts are personable without being over-the-top, and they've created a community around the website. By this I mean there are discussions around each lesson on the website where users can leave comments and questions, and the hosts of the lessons and other employees will personally answer your questions. The lessons themselves are all free to download, but you need a paid subscription to get the extra materials (including the written transcript of the lesson dialogues). I'm familiar with some of the audio lessons you can buy at the store (Pimsleur, Rosetta Stone, etc.) and have not been particularly impressed with them.
My favorite online dictionary. I particularly like the example sentences and the great tool for looking up characters by drawing them.
Another online dictionary that is actually aimed at Chinese people learning English, but is also great for seeing the words you look up used in example sentences (all with English translations).
A useful site for reading Chinese, in which you can copy and paste several sentences of Chinese text and have them "annotated," meaning that you can see the definition of each word or phrase when you hover the mouse pointer over it. Much quicker than looking up each word in the dictionary individually. The only downside is that for words that have multiple meanings, the site makes the best guess of the meaning relevant to the sentence and shows you only that definition, so if it guesses wrong you are going to have to look up the word in the dictionary anyway.
Oxford Starter Chinese Dictionary
The first dictionary I used, which is great for the beginner as it includes examples and notes about how to use words, lots of information on measure words, and sections devoted to things like talking about "time" or "musical instruments" in Chinese. Apparently there is a new version called the Oxford Beginner's Chinese Dictionary, which I'm sure is worth checking out. The dictionary I use now is the confusingly named Pocket Oxford Chinese Dictionary, which is excellent but not at all pocket size. All of these dictionaries use simplified Chinese characters.
Reading and Writing Chinese
A great reference book for learning characters, as it does the best job of any book I've seen of actually explaining the logic and meaning behind the characters. Be sure to pick up the simplified character version for mainland China and the traditional character version for Hong Kong and Taiwan.
Intensive Spoken Chinese
The first textbook I used, and an excellent beginner's textbook for learning the spoken language (the characters are included as well, but not emphasized). The first book in a series, which is followed by The Most Common Chinese Radicals and Rapid Literacy in Chinese. The last two are also recommended, and the series is widely available for a low price in the foreign language bookstores of large Chinese cities.
New Practical Chinese Reader
A five-volume series of textbooks that I have encountered through my Peace Corps coworkers, who have been supplied with the books for their language training. I haven't had the chance to use the books much myself but I've liked what I've seen. I'm not sure that they are available in China, and I haven't been completely satisfied with any of the more advanced textbooks I have bought here.