King David's lineage was foretold in the actual name of Ruth: Berachot 7b
Gd rewarded the Jewish midwives in Egypt with houses of royalty, as King David was known as a descendant of Efrat, and Efrat was another name for Miriam: Sotah 11b
King David was a descendant of Tamar; she merited to be his ancestress as a result of her modesty: Megillah 10b; Sotah 10b
David was known as "Michtam," because he was humble [Mach] and perfect [Tam] with others, or because he was born circumcised [Makkato Tam], or because his humility was perfect both when he was lowly and when he became king: Sotah 10b
David's Merit saved Chizkiyah and Jerusalem: Berachot 10b
King David as a True Supporter of the Generation: Yoma 86b
Daniel and King David as two "Great Men of their Generations": Megillah 15a
According to Abbaye, Rabbah, Rav, Rebbe and King David habitually slept like horses, meaning that they napped for 60 "breaths": Succah 26b
King David was upset, in the bathhouse, when he saw that he had no Mitzvot around him; he was reassured when he remembered his circumcision: Menachot 43b
King David taught from the ground in the Study Hall, not from a seat atop cushions: Moed Katan 16b
Parents used to bring their daughters to King David: Megillah 12b
His Piety, in disregarding his own honor to serve law: Berachot 4a
Meal he distributed to the nation, when the Ark was brought back to Jerusalem: Pesachim 36b
King Saul was anointed from a pitcher of oil, King David and King Shelomo from horns of oil: Megillah 14a
King David's ability to appeal Divine decrees: Moed Katan 16b
King David as one of the 7 "Shepherds" - King David, flanked on the right by Adam, Seth and Methuselah, and on the left by Avraham, Yaakov and Moshe: Succah 52b
King David descended to the core of his learning, and merited, "Those who have of You see my and are glad." King Saul did not, and so "Where he turned he created evil.": Eruvin 53a
The walls of the Temple sank into the ground, rather than be destroyed by the enemy, so that King David's work shouldn't be used by his foes: Sotah 9a
King David dedicating the floor of the azarah and heichal for the Beit haMikdash: Tosafot Zevachim 24a "ho'il"