I made up a diaper change song to Raffi's "bath time" song. Geez, I don't think I can remember the words now (I am getting old, I guess - lol). It started with "the diaper is wet, wet, wet, so we're set, set, set, get that boy undressed, it's dry dipe time" (short for diaper).
And a toothbrushing song or two (my youngest won't let me sing them anymore though - teehee). Let's brushabrushabrushabrush your teeth was to "She'll be coming round the mountain).
I would also sing songs while we were walking the dog, classics, Raffi, Trout Fishing in America (if you haven't heard them, look them up, they're hysterical), or even songs not for kids, and Christmas carols (mostly in the right time of year, although I would occasionally throw them in other times when my creativity was low).