If all you want to do is switch multicast traffic within a single VLAN, then there is not much to do (and no routing is required).
All you need to do is the following:
1) Create the VLAN on switch/es
vlan 200
name Multicast_VLAN
2) Turn on IGMP snooping. This will ensure that multicast packets are only switched to ports that have subscribed to the multicast group and not flooded to all ports configured on that VLAN.
ip igmp snooping vlan 200
However, if you want multicast between VLANs you need multicast routing and something like protocol independent multicast (PIM).
In this case you configuration would look something like the following (in addition to the configuration above):
ip routing
ip multicast-routing
interface loopback0
ip address 192.168.100.1 255.255.255.255
interface vlan 200
ip address 192.168.200.1 255.255.255.0
ip pim sparse-mode
interface vlan 300
ip address 192.168.201.0 255.255.255.0
ip pim sparse-mode
ip pim rp-address 192.168.100.1
For more information on configuring multicast routing see http://www.cisco.com/en/US/customer/products/sw/iosswrel/ps1826/products_configuration_guide_chapter09186a00800877cb.html