How to defend against optimized charge?

[Ganurath]

Isn't there a spell somewhere that conjures a 5' box or something as an immediate action?

Blockade, Complete... Scoundrel, I believe. If not, then Complete Adventurer. Either way, though, not the best option of a melee generalist.

My recommendation is Martial Study for either Counter Charge, or Mighty Throw if you can consistently get the initiative to ready an action. Strength checks may be nightmarish here, but opposed Dexterity puts the ball in your court. Or, a level dip in Swordsage to pick up all sorts of options. Nothing says "screw uberchargers" like Setting Sun Style.