Gd punishing for not fulfilling a potential positive commandment: Kiddushin 39b [2x]; Menachot 41a
ha'oseik b'mitzvah patur min hamitzvah - one who is performing a mitzvah is exempt from other mitzvot
If one is already performing Mitzvah X, he is exempt from Mitzvah Y: Berachot 11a, 16a-b, 19a; Pesachim 55a; Succah 10b, 25a-26a; Ketuvot 6b; Nedarim 33b-34a
The Source for this principle: Succah 25a-b
We avoid creating such a conflict, if possible: Berachot 19a
Whether this applies for a person marketing Torah scrolls, phylacteries or mezuzah scrolls: Succah 26a
Active Mitzvah vs. Active Mitzvah or prohibition - Aseh Docheh Lo Taaseh
Active Mitzvah vs. prohibition: Shabbat 132b; Beitzah 8b
Active Mitzvah vs. prohibition and Active Mitzvah: Shabbat 132b, 133a; Rosh HaShanah 32b; Beitzah 8b; Bava Metzia 30a, 32a
Active Mitzvah vs. two prohibition: Temurah 4b
An active public Mitzvah, vs. a personal active Mitzvah: Moed Katan 14b
A Mitzvah involving one's personal body: Kiddushin 29b
A Mitzvah which will not be fulfillable later: Kiddushin 29b
Extrapolating priority from the juxtaposition of Mitzvot in the Torah: Kiddushin 29b
Requiring that the Active Mitzvah be fulfilled with the Violation of the prohibition, immediately: Shabbat 132b; Beitzah 8b
Active Mitzvah vs. prohibition where both the Active Mitzvah and the prohibition can be fulfilled: Shabbat 133a; Kiddushin 40a
Active Mitzvah with a punishment of Divine Ex-Communication, vs. an ordinary Active Mitzvah: Pesachim 59a
Where one of the Mitzvot could be fulfilled by another individual: Berachot 14b; Kiddushin 32a
Where one Mitzvah is more central to an act than the other is: Succah 56a
Whether the more common Mitzvah ["Tadir"] has precedence: Succah 54b, 56a; Pesachim 114a; Megillah 29b; Menachot 49a
Whether the holier entity has precedence: Menachot 49a
Gauging which to do, if one involves a Holier item, and the other is more Common: Menachot 49a-b