General Linguistics:
Linguistlist: http://linguistlist.org
Ethnologue: http://www.ethnologue.com/web.asp
Omniglot: http://www.omniglot.com
Glossary of linguistic terms: http://www.sil.org/linguistics/GlossaryOfLinguisticTerms
IPA symbols: http://www.phon.ucl.ac.uk/home/wells/ipa-unicode.htm
Grammar Instruction: http://teach-grammar.com
Early Indo-European texts:
LRC - UTexas, Austin: http://www.utexas.edu/cola/centers/lrc/ietexts
Early Germanic sources:
Library at Septentrionalia: http://www.septentrionalia.net/etexts/index.php
Old English sources:
Bosworth & Toller OE Dictionary: http://beowulf.engl.uky.edu/~kiernan/BT/Bosworth-Toller.htm
Peter Baker (U of V): Old English & OE Aerobics Anthology
http://www.wmich.edu/medieval/resources/IOE/index.html
http://www.oldenglishaerobics.net
Dictionary of Old English Project: http://www.doe.utoronto.ca/
Beowulf (& other OE) manuscript (Cotton MS Vitellius A.XV: http://www.bl.uk/manuscripts/FullDisplay.aspx?index=0&ref=Cotton_MS_vitellius_a_xv
Corpus of Anglo-Saxon Stone Sculpture: http://www.ascorpus.ac.uk/
Middle English sources:
Middle English Compendium: http://quod.lib.umich.edu/m/mec
Middle English (TEAMS): http://www.lib.rochester.edu/camelot/teams/tmsmenu.htm
Anglo-Norman sources: http://www.anglo-norman.net
Additional Medieval Studies sources:
Labyrinth: http://labyrinth.georgetown.edu
O.R.B for Medieval Studies: http://the-orb.net
Oxford Text Archive: http://ota.ahds.ac.uk
Facsimiles: Early Mss. Oxford Univ. http://image.ox.ac.uk/list?collection=corpus
Early Modern and Modern Corpora:
Corpus of Contemporary American English: http://corpus.byu.edu/coca
Corpus of Historical American English: http://corpus.byu.edu/coha
British National Corpus: http://www.natcorp.ox.ac.uk
GerManC (German 1650-1800): http://www.ota.ox.ac.uk/desc/2544
Standard Dutch Grammar: http://ans.ruhosting.nl/
General Interests:
Etymology (format is playful): www.mysteriesofvernacular.com
British Library Digitized Manuscripts: http://www.bl.uk/manuscripts/About.aspx