Who knows twenty-six?
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26 are the verses of Hallel HaGadol (Hodu LaShem Ki Tov)
the 26 generations that Hashem sustained with His Chesed (because they did not have the merit of the Torah. See Jeremy's answer.)
(T.B. Pesachim 118)
There is no word in Megillat Esther with the gematria 26.
26 is Hashem (in the Heaven and the Earth. ooh ahh, ooh ooh ahh!) gematriah of tetragrammaton
26 generations to Moshe Rabbeinu (10 to Noach plus 10 to Avraham, then Yitzhak, Yaakov, Levi, Kehat, Amram, Moshe)
26 are the knots and strings on the two front Tzitziyos (which the Gr"a says is the meaning of "You shall see them and remember...".)
26 are the years of peace that Sodom and its sister cities enjoyed (from after the war with the four kings - Gen. 14 - until their destruction). (Shabbos 10b-11a)
26 is the Gematria of the parts of One. (Alef is made of two Yuds and a Vav.)
26 are the years during which the Romans treated their allies, the Chashmonaim, as equal partners. After that they began to lord it over them, culminating in the eventual Roman takeover of Eretz Yisrael. (Avodah Zarah 8b, 9a)
26 is the number of generations it took to recieve the Torah.
26 is the number of times someone outside of the Land of Israel will have asked "mi yodeya" as part of the Pesach seder (excluding repetitions for fitting a particular tune).