I18n (Internationalization)

Unicode

• The Unicode Character Code Charts By Script
• Unihan Radical-Stroke Index (Chinese, Japanese, Korean)
• Unicode Character Database
• Text Boundaries (Unicode Standard Annex #29)
• FAQ - UTF-8, UTF-16, UTF-32 & BOM (Unicode.org)
• Unicode Nepali Converter

XML Specifications

• Extensible Markup Language (XML) 1.0 (Third Edition)
• XLIFF (XML Localization Interchange File Format) 1.1 Specification
• TMX (Translation Memory eXchange format) 1.4b Specification
• SRX (Segmentation Rules eXchange format) 1.0 Specification
• OpenDocument Format for Office Applications (OpenDocument) v1.0

Other

• Punycode: A Bootstring Encoding of Unicode for Internationalized Domain Names in Applications (IDNA)
• IANA Official Character Set Names
• ISO 639 Language Codes
• ISO 3166 Country Codes
• Tags for the Identification of Languages (RFC 3066; obsoletes 1766)
• RFC 3066 Language Code Assignments
• GNU 'gettext' utilities
• Firefox Extension Development Tutorial :: Localization
• XUL Tutorial: Localization
• Adding libiconv Support for the IMAP Variant of UTF-7

Miscellaneous

• Good Versus Well (Thank you, Grammar Girl!)
• 1337 (Leet)
• 五笔字型 Wubizixing for Speakers of English (Popular Simplified Chinese input method)
• Text Messaging Abbreviations