the lil three card combo can produce a large amount of blue mana but alas you have to wait for shadowmoor to become standard legal.
-now if you have 'Leechbonder' in play enchanted with 'Utopia Vow'
you can tap him for one blue mana, then you can use the one blue mana to untap him, well if you also have 'Mana Reflections' in play tapping him produces two blue mana, and untapping him only uses one blue mana leaving one left over, voila 'arbitrarily large amount' of blue mana.
The question i pose is what to do with all that blue mana