For the benefit for any other newbies with the same problem, the simple solution was to define a default route on the 2505 pointing to the Linksys gateway to the outside world:
ip route 0.0.0.0 0.0.0.0 192.168.1.1
Before:
Routesaurus#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
Gateway of last resort is not set
C 192.168.1.0 is directly connected, Ethernet0
After:
Routesaurus#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
Gateway of last resort is 192.168.1.1 to network 0.0.0.0
C 192.168.1.0 is directly connected, Ethernet0
S* 0.0.0.0 0.0.0.0 [1/0] via 192.168.1.1