I would use policy-based routing on the 3560 to accomplish this.
What IOS version are you using?
You will need to configure the SDM template to routing in order to enable PBR.
Setting the SDM template to routing is quite simple. It involves the configuration command:
sdm prefer routing
then a reload
http://www.cisco.com/en/US/products/hw/switches/ps5528/products_configuration_guide_chapter09186a00805b8490.html
PBR can be configured here:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfindep.htm#wp1001398
Basically you will need to match the source vlan in the route-map and set the next-hop to the the desired gateway. Finally, apply this to the source vlan interface.
Hope this helps.
Michael
Cisco TAC