Much of this slots into time outside work rather than the workday itself.

• walk a different route to a destination
• pick an algorithm and walk with no destination (eg: straight until you hit a light not in your favor, then turn. Works in urban envs)
• go somewhere you don't normally go. Eg: library, different coffee shop, that little art store you always see
• go to the library. Walk along the shelf with eyes closed and pick a book at random.
• pick a genre of music you never listen to. Listen to it.
• cook or prepare a meal unlike your normal fare
• go to a thrift store. Buy a cheap article of clothing you wouldn't normally wear. Wear it. See how it feels
• find free or cheap art (music, theater, whatever) in your area. Go.
• journal. Spend a few minutes writing down your day's details
• hit wikipedia's random article button. Read it.