1. General etymological dictionaries and databases (arranged by language family)
1.1. Portal site (multiple language families)
a.
Databases - Portal site, 60+ etymological databases, a.o. Indo-European, Altaic, Sino-Tibetan, Dravidian, Afro-Asiatic, Japanese, and many more language families (and subfamilies) and language isolates [in English]
1.2. Altaic
Turkish
a.
http://socrates.berkeley.edu:7037/cg...TELLsearch.cgi - Turkish Electronic Living Lexicon, general dictionary of modern Turkish with etymological explanations [in English]
b.
http://www.nisanyan.com/sozluk/search.asp?w=kof&x=26&y=8 - not a 100% reliable [in Turkish]
1.3. Austroasiatic
Vietnamese
a. Chinese-Vietnamese Etymology: Tunguyen Han-Nom - Từnguyên HánNôm (haylà TiếngNôm có gốcHán, The Etymology of Nôm of Chinese Origin, ho) [in Vietnamese, Chinese, English]
1.4. Austronesian
Indonesian
a.
Indonesian Etymology Database - Indonesian Etymology Database [in Indonesian, English]
1.5. Indo-European languages
a.
http://www.indo-european.nl/\index2.html - Portal site, 23 etymological databases of various (older) IE languages and sub-families [in English]
b.
The American Heritage Dictionary of the English Language, Fourth Edition. 2000 - C. Watkins' list of PIE roots (related to English) [in English]
Proto-Indo-European
a.
http://homepage.uibk.ac.at/~c30310/idgwbhin.html - Köbler, Gerhard [in German]
b.
http://www.indo-european.nl/cgi-bin/startq.cgi?flags=endnnnl&root=leiden&basename=%5Cdata%5Cie%5Cpokorny - Pokorny's classic PIE dictionary (slightly outdated) [in English]
c.
WordReference Forums - PIE roots and tree of reflexes -- experimental site under development.
Baltic
Lithuanian
a.
http://www.lkz.lt/startas.htm - [in Lithuanian]
Celtic
Gaelic
a.
MacBain's Dictionary - A. MacBain's
Etymological Dictionary of the Gaelic Language [in English]
Germanic
Proto-Germanic
a.
http://lexicon.ff.cuni.cz/pdf/pgmc_torp/pgmc_torp.pdf - A. Fick's
Wortschatz der germanischen Spracheinheit, 1909 [pdf] [in German]
b.
http://homepage.uibk.ac.at/~c30310/germwbhinw.html - Köbler, Gerhard [in German]
c.
Germanic Lexicon Project - Germanic Lexicon Project [in English]
Dutch
a.
http://gtb.inl.nl/ - Woordenboek der Nederlandse Taal, with etymological notes [in Dutch]
English (and derived languages)
a.
http://www.etymonline.com/ - [in English]
b.
http://www.dsl.ac.uk/index.html - Searchable dictionaries from this site:
SND, Scottish National Dictionary, documenting Modern Scots, i.e. 1700-present and
DOST, Dictionary of the Older Scottish Tongue, documenting Middle Scots.
German
a.
http://homepage.uibk.ac.at/~c30310/derwbhin.html - Köbler, Gerhard [in German]
b.
http://dwb.uni-trier.de/Projekte/DWB/ - Grimm's dictionary [in German]
c.
http://www.mhdwb-online.de/ - Middle High German dictionary [in German]
Swedish
a.
http://g3.spraakdata.gu.se/saob/ - General dictionary of modern Swedish with etymological explanations [in Swedish]
b.
http://runeberg.org/svetym/ - Old dictionary, 1922 [in Swedish]
Greek
'Mycenean' Greek
a. http://www.projethomere.com/ressources/linearb.pdf - Linear B glossary [pdf] [in English]
Greek
a.
http://www.komvos.edu.gr/dictionaries/dictonline/DictOnLineTri.htm - General Greek dictionary with etymological notes [in Greek]
Italic (and Romance)
Catalan
a.
http://www.grec.net/home/cel/dicc.htm - Catalan dictionary with etymological notes [in Catalan]
French
a.
http://atilf.atilf.fr/academie.htm - Dictionary of the Académie Française, with etymological notes, 8th edition [in French]
b.
http://francois.gannaz.free.fr/Littre/accueil.php - [in French]
c.
http://www.cnrtl.fr/etymologie/ - French etymology excerpted directly from the TLFi dictionary (Trésor de la Langue Française Informatisé) [in French]
Galego
a.
http://www.agal-gz.org/estraviz/ - General Gelego-Portuguese dictionary with etymological notes [in Portuguese]
Italian
a.
http://etimo.it/ - Slightly outdated Italian etymological dictionary [in Italian]
Occitan
a.
http://etymologie-occitane.chez-alice.fr/ - history of Occitan words (about 1500 words now)
Portuguese
a.
http://www.agal-gz.org/estraviz/ - General Galego-Portuguese dictionary with etymological notes [in Portuguese]
Romanian
a.
http://dexonline.ro/ - General Romanian dictionary with etymological explanations [in Romanian]
Spanish
a.
http://www.elcastellano.org/palabra.php - Limited etymologic dictionary [in Spanish]
b.
http://www.rae.es/RAE/Noticias.nsf/Home?ReadForm - General dictionary of the Spanish Academy with etymological notes [in Spanish]
Slav(on)ic
Czech
a.
http://www.sweb.cz/corpus/slovnik.htm - Rather rudimentary [in Czech]
Russian
a.
http://starling.rinet.ru/cgi-bin/main.cgi?root=/usr/local/share/starling/morpho&morpho=1 - Ozegov, Zalizniak, Vasmer [in Russian]
b.
http://www.oomnik.org/korneslov - Lexical roots and derivatives [in Russian]
c.
http://www.vasmer.narod.ru/ - [in Russian]
1.6. Sino-Tibetan
Chinese
a.
http://www.chineseetymology.org/ - Chinese
character etymology (as with most character etymological dictionaries: to be taken with a grain of salt) [in English]
1.7. Uralic
Estonian
a.
http://www.eki.ee/dict/raun/ - Limited [in Estonian]