Watching Inuyasha is like watching the original Sailor Moon.The shortest animes I know is Puella Magi Madoka Magica and Devil's Line.
25 Episode anime:
Princess Tutu
Accel World
How Not to Summon a Demon Lord
Trinity Blood
Wallflower
Flying Witch
Drifters
both Sword Art Online and Vampire Knight are broken up into seasons of course SAO is ongoing.