All of the episode titles in season 8 are lines that were said in season 1."Nostalgia's a bitch" was a line said by Damon to Anna in season one episode 19.
While Bonnie and Caroline are standing in the Mystic Grill discussing forgiving Damon, Caroline tells Bonnie "Say that once more with feeling". In the TV series "Buffy the Vampire Slayer" season six, episode 7 is titled "Once more, with feeling". In the episode, a demon comes to town and turns the whole city of Sunnydale into a musical.
When in Damon's subconscious, Bonnie shows Caroline a newspaper showing two people missing because of an 'animal attack' - it's the couple Damon killed in the opening scene of the pilot episode