American Heritage Dictionary (from Yahoo)

http://education.yahoo.com/reference/dictionary/index.html

Merriam-Webster Online

http://www.m-w.com/netdict.htm

OneLook Dictionary (multiple dictionaries)

http://www.onelook.com/

OneLook Reverse Dictionary (finds your word/s in the defintion)

http://www.onelook.com/reverse-dictionary.shtml

Dictionary.com (multiple dictionaries)

http://www.dictionary.com/

YourDictionary.com (uses American Heritage)

http://www.yourdictionary.com/

Cambridge Dictionaries Online (simplified for English learners) (note options in the pull-down menu)

http://dictionary.cambridge.org/

The Newbury House Online Dictionary (simplified for English learners)

http://nhd.heinle.com/

SPECIALIZED DICTIONARIES:

The Phrase Finder -- Phrases, Sayings, and Idioms

http://www.phrases.org.uk/meanings/index.html

Cambridge International Dictionary of Idioms

http://dictionary.cambridge.org/Default.asp?dict=I

RhymeZone (rhyming dictionary & also finds synonyms, antonyms, homophones, related words, etc.)

http://www.rhymezone.com/

Medical Dictionary (from Medicinenet.com)

http://www.medterms.com/script/main/hp.asp

Encyberpedia (multiple specialized dictionaries)

http://www.encyberpedia.com/glossary.htm

Infoplease (Encyc., Dict. & more)

http://www.infoplease.com/

Bartleby.com (Encyc, Dict. & more)

http://bartleby.com/

Yahoo! Reference

http://education.yahoo.com/reference/

Refdesk.com (Facts & reference)

http://refdesk.com/

Infoplease Almanac

http://www.infoplease.com/almanacs.html

Official Statistics on the Web (from Univ. of Auckland)  (statistics about countries/regions of the world)

http://www.offstats.auckland.ac.nz/  

Common Errors in English

http://www.wsu.edu/~brians/errors/

Guide to Grammar and Writing

http://grammar.ccc.commnet.edu/grammar/

Oxford Dictionaries -- Better Writing (tips on grammar, spelling, puncutation, easily confused words, etc.)

http://www.oxforddictionaries.com/page/betterwriting/

Univ. at Albany Style Guides (guidelines for citing sources in MLA, APA, and Chicago styles)

http://library.albany.edu/usered/cite/index.html

Conversion & Calculation Center

http://www.convertit.com/Go/ConvertIt/

Yahoo -- Weights & Measures

http://education.yahoo.com/reference/weights_and_measures/

Yahoo -- Online converters

http://dir.yahoo.com/Science/Measurements_and_Units/Conversion/Online_Converters/

Merriam-Webster's Atlas

http://www.m-w.com/maps/moremapsnyt.html

Infoplease Atlas

Infoplease Atlas -- Map Index

http://www.infoplease.com/atlas/

http://www.infoplease.com/atlas/mapindex.html

Lonely Planet Destinations

http://www.lonelyplanet.com/destinations/

World Maps from About.com

http://geography.about.com/library/maps/blindex.htm

WorldAtlas.com

WorldAtlas.com -- Quick world facts

http://www.worldatlas.com/aatlas/world.htm

http://www.worldatlas.com/geoquiz/thelist.htm

Microsoft Expedia Maps

http://maps.expedia.com/QuickMaps.asp

National Geographic Map Machine

http://www.nationalgeographic.com/maps/index.html

Xpeditions -- Nat'l Geographic's printable maps

http://www.nationalgeographic.org/xpeditions/atlas/

Internet Public Library – Magazines by topic (click on "Magazines" tab)

http://www.ipl.org/div/news/  

Internet Public Library -- Online Newspapers

http://www.ipl.org/div/news/

RefDesk.com -- Newspapers 

http://www.refdesk.com/paper.html

Today's Front Pages (shows an image of the front page of each newspaper's print version)

http://www.newseum.org/todaysfrontpages/

The Quotations Page

http://www.quotationspage.com/

Bartleby.com -- Quotations

http://www.bartleby.com/quotations/

Famous Quotes and Authors

http://www.famousquotesandauthors.com/

Yahoo! - Reference:Quotations

http://dir.yahoo.com/reference/quotations

About.com -- Quotations

http://quotations.about.com/

Quoteland.com

http://www.quoteland.com/

QuoteWorld.org

http://www.quoteworld.org/

 LitQuote -- Literary Quotations

http://www.litquotes.com/quote_topic.php

Quotebilia

http://www.quotebilia.com/