SHIKANTAZA, or "just sitting," is alert nonselective attention which neither pursues nor suppresses thoughts, sensations, etc., but, rather, gives alert detached attention to whatever arises in and vanishes from consciousness.

~ from www.angelfire.com/electronic/awakening101/shikantaza.html

Wow! I really like that description. Right now in my practice it just seems to resonate with me and describe pretty well for me what shikantaza is.