We spent many days poring over manuscripts, limited edition photo-reproductions and microfilms in libraries to check manuscript variants back in 1976 when we were completing our PhD at Brown. Things are different today. Here are a few useful links:
- Mishnah and Shas
- Talmud with Rashi and Tosefot
- A Dictionary of the Targumim, the Talmud Babli and Yerushalmi, and the Midrashic Literature. Compiled By Marcus Jastrow, Ph. D. Litt. D. (in PDF format): Volume one, Volume two and here.
- Rambi: The Index of Articles on Jewish Studies
- The Comprehensive Aramaic Lexicon from HUC
- The Jewish National University Library has online the Kaufman, Parma and Cambridge manuscripts of the Mishnah and the Munich (linked to the Bayerische Staatsbibliothek), Florence and Paris manuscripts of the Talmud
- Online Soncino Translation of the Babylonian Talmud at Halakhah.com