if you have a 4507 with a standard image is it a layer 3 switch? and if not would it be worth it to upgrade to an enhanced image for a medium sized business - small webfarm/dmz - 40 very small remote site and under 400 users?
You would configure L3 inter-vlan routing as you would on any L3 switch ie.
1) Create your vlans at layer 2 eg.
4500(config)# vlan 10
4500(config-vlan)# name v10
etc for all vlans.
2) Create your L3 SVI's for your L2 vlans eg.
int vlan 10
ip address 192.168.5.1 255.255.255.0
int vlan 20
ip address 192.168.6.1 255.255.255.0
clients in vlan 10 would have their default-gateway set to 192.168.5.1 and clients in vlan 20 would have their default-gateway set to 192.168.6.1
3) Because these are directly connected interfaces on the 4500 then they will automatically be routed. I can't remember off the top of my head but if not then type in config mode
4500(config)# ip routing
4) Add a default-route on the 4500 pointing to the router
ip route 0.0.0.0 0.0.0.0
5) Add routes to the router for each vlan pointing back to the 4500.