General

• China Highlights: travel website with lots of information about culture, as well as recommendations and tips for traveling in China.
• Taiwan Ministry of Culture: tons of resources, articles, and exhibitions for those interested in Taiwan.
  • Taiwan Culture Portal: find resources about Taiwanese film, art, performing arts, literature, and more.
• Chinese Calendar Online: Resorces relating to the Chinese lunar calendar (农历 nónglì). You can see today's date, convert days, learn the basics of the lunar calendar, and learn the dates of traditional holidays. Available in English and Traditional Chinese.
• Chinesenewyear.net: lots of information about Chinese astrology, holidays, and traditions.

Arts

• National Palace Museum Website in Beijing, China (故宫博物院): available to browse in Simplified Chinese, English, and "kids version" (青少版).
• National Palace Museum Website in Taipei, Taiwan (國立故宮博物館): traditional Chinese, English, and Japanese.
• Art Virtue: a cool website about Chinese calligraphy (书法 shūfǎ) with tutorials, history, and resources. The website is available in English and simplified characters.

Food

• Meishi China (美食天下): find Chinese recipes (in Simplified Chinese only).
• Eating China: read about Chinese food history and culture and find recipes in English.

Regional differences

• Phonemica: a large collection of recordings from different Chinese-speaking regions around the world, in which contributors add recordings of "regional lore, nursery rhymes & childhood games, preparation of local foods, humorous anecdotes, local history," and more. You can use it to hear the sounds of different accents and dialects based on region.

Social Justice

• Asia Society: organization covering and analyzing Asian politics, art, education, and more (not just China specifically).
• Council of Indigenous Peoples (原住民族委員會): Learn about Taiwanese indigenous peoples, available in Traditional Chinese and English.
• OutChina: LGBT stories and resources from China. They have a lot of cool resources, including a podcast in Mandarin and a YouTube channel about the social issues regarding LGBT people in China. Bilingual in English and Simplified Chinese.

• Chinese Measurement Converter: easily convert between English, metric, and traditional Chinese units of measure.
• Mandarintools.com: there are several tools helpful for learners on this site, including language learning plugins, money conversion tools, a way to repair corrupted Chinese text, and more.
• Chinese Converter: this website has several tools. It includes online Chinese input methods, a converter for simplified to traditional characters and vice versa, a tool that reads text aloud, a way to convert Chinese characters to Pinyin, and others. But be aware that the results on this website are not 100% accurate.