Not really all that often since I'm prone to accidentally managing to get soap in my mouth somehow, I'm more the person who does it when I have a fair amount of chore to do. If it's a slow day, I'll bring some tunes into work since folks seem to like. One guy gets way into songs he knows and belts them out for everyone to head xD
The songs I sing just randomly rotate, but a single one that I keep wanting to sing will stay there for awhile. This is the one that's take that slot currently: