I've used various methods for scripting telnet sessions under unix, but the simplest one is probably a sequence of echo and sleep commands, with their output piped into telnet. Piping the output into another command is also a possibility.
Silly example
(echo password; echo "show ip route"; sleep 1; echo "quit" ) | telnet myrouter
This (basicallly) retrieves the routing table of a Cisco router.