History
Electronic Resources in East Asian History - Project of the Institute of East Asian Studies, Center for Chinese Studies, and Electronic Cultural Atlas Initiative. Includes: Shanghai In Images, Beijing In Images, Maps of Shanghai, Maps of Kyoto, Historical Chinese Postcard Project: 1896-1920. I am particularly fascinated with the postcards project, which were collected by a French scholar. Besides the staged photographs (and the subjects in China that were chosen), it's also interesting to read what people wrote back home. The Shanghai In Images project is also a good source, and one that's been reviewed for the World History Matters project.

Language Learning
Chinese Podcasts - Language learning through free daily podcast lessons that encompass various topics, from news pieces to common "swear words" you'll encounter. Levels from novice - advanced.

Web/Techie
CHNM Tools - CHNM has developed several tools useful for scholars. The web scrapbook is particularly useful for sharing images and websites with other people. Scribe is a free filemaker tool for collecting and taking notes (and storing source information). A former co-worker who received her PhD at GMU developed the tool in order to keep track of research while writing her dissertation. I've started using it for my own notes.