please I need your help.
my english is not good enough.
we want to build a LAN with 2 switches cisco 3750 24ps-e (this switch support ip routing) and 1 switch ME 3400G 2(aggregation switch).
we want to build 2 Vlan in this LAN. Do we have to use a router if we want communication between the Vlans?
No you don't need a router because as you say the 3750 supports ip routing and one (or both) of your 3750 switches can be used for the inter-vlan routing.