Grammars and dictionaries

Biblical Hebrew: Gesenius dictionary, English translation of 1906. Grammar of Gesenius-Kautzsch-Cowley, as a module in the free Bible program E-Sword.

Postbiblical Hebrew and Aramaic: Jastrow, Dictionary...; Margolis, Manual of the Aramaic Language of the Babylonian Talmud.

Arabic: E.W. Lane, Arabic-English Lexicon.

Syriac: J. Payne Smith, Compendious Syriac Dictionary; download PDF of the same; W. Jennings, Lexicon to the Syriac New Testament (download PDF). Nöldeke's Grammar download as PDF.

Coptic: W.E. Crum, Coptic Dictionary.

Akkadian: Association Assyrophile de France, Akkadian Dictionary.

Hittite: Association Assyrophile de France, Hittite Lexicon.

Latin: W. Whitaker, Words.

Biblical Greek page of Zack Hubert, user-friendly interface at Tyndale (choose Greek (OT & NT)).

Many modern languages: The Free Dictionary, French, Spanish, Russian etc.