Avraham serving others, although he was greater than them: Kiddushin 32b
Tamar went to the entrance of Avraham's tent, which was a place to which everyone looked, and so it was called "The Entrance of the Eyes" [alternative explanations for the name are presented, as well]: Sotah 10a
Avraham established an "Eshel" for travelers; this was either an orchard or an inn: Sotah 10a
Avraham would tell his visitors not to thank him for the hospitality, but to thank Gd for it: Sotah 10a-b