The following sites contain links to online reference tools: almanacs, encyclopedias, fact books, dictionaries, thesauri, quotes, directories, statistics, atlases, grammar guides, calendars, weights & measures, more.

See also Reference databases.

General Sites

• Refdesk.com: The Single Best Source for Facts on the Net

Acronyms

• Acronym Finder - 252,000+ acronyms, abbreviations, and their definitions.

Calculators & Converters

• Approximate Conversions from Metric Measures - How to convert Metric measurements into other units.
• Approximate Conversions to Metric Measures - How to convert units of measurement into Metric units.
• CalculatorPLUS.com - Free business & financial calculators includiing mortgage loan, credit card, insurance, interest rate, savings, refinance, retirement, and auto finance.
• ConvertIt.com - Measurements, exchange rates, time zones, calculators, more.
• Currency Converter - Multilingual Foreign Exchange calculator.
• DollarTimes.com - Financial calculators covering home & car loans, investment & savings, and personal finance.
• Interactive Units Converter - Convert weight, temperature, speed, etc.

Dictionaries

• Dictionary.com and Thesaurus.com
• Foreign Language Dictionaries - List compiled by Yahoo!
• Lexicool.com - More than 7,000 bilingual and multilingual dictionaries.
• OneLook® Dictionaries - Searches more than 800 online dictionaries.
• yourDictionary.com - 1800+ general and subject-specific dictionaries in more than 250 languages.

Directories

• Infobel - Links to online telephone directories.

Population Counts

• Population Counts - Current U.S. and world population estimates from the U.S. Census Bureau.

Time Zones

• World Time Zones - Search for a city/place to find the correct time.

Zip Codes

• ZIP Codes - ZIP Code lookup from the U.S. Postal Service.