If you still want to configure outbound NAT for your S2500 Mobility Access Switch, it is described in the User Guide, and basically comes down to (if vlan 10 is your LAN, and vlan 255 is your outbound interface):
(host) (config) #interface vlan 10
(host) (vlan 10) #ip nat inside
(host) (config) #interface vlan 255
(host) (vlan "255") #ip nat outside
(host) (config) #show interface vlan 255
VLAN255 is administratively Up, Line protocol is Up Hardware is CPU Interface, Address is 00:1a:1e:0c:72:40 Description: 802.1Q VLAN
Internet address is 192.168.100.1, Netmask is 255.255.255.0 IPV6 link-local address is fe80::1a:1e00:640c:7240
Global Unicast address(es):
Routing interface is enabled, Forwarding mode is enabled Interface is source NAT'ed
Interface is egress source NAT'ed
Directed broadcast is disabled
Encapsulation 802, Loopback not set
Interface index: 50331658
MTU 1500 bytes
Metric 10
Probe Name: test, Probe Status: Down
With NAT pools you can set up even more advanced NAT. Please read the notes and limitations in the user guide.