Sure, my initial inclination here is to say "fresh baked bread", and while that might be true mostly (along with fresh brewed coffee), I deep cleaned our house last evening. I Cloroxed the bathtubs, sink, disposal, outdoor furniture, etc. This morning, I awoke to the faint smell of that "Clorox" and it say's to me, "clean, clean, clean". I love my house that clean.
So, what smell (common or unusual) makes you happy sometimes?