Minors: Berachot 20a-b
Eved Kenaani: Berachot 20a-b
Exemption for a Groom before initial sexual relations: Berachot 11a, 16a-b; Pesachim 55a; Succah 25a; Ketuvot 6b
Exemption For a Groom when marrying a Widow: Berachot 11a, 16b; Succah 25a
Requirement for Members of a wedding party during the First Week of Marriage: Succah 25b-26a
Exemption for an Onein, for escorts of a Coffin and for those involved in post-burial consolation: Berachot 17b-18a, 19a-b
Exemption for someone engaged in a Mitzvah: Berachot 11a, 16a-b, 19a; Ketuvot 6b
Exemption for being generally busy: Berachot 11a; Succah 25a; Ketuvot 6b