[masraum]

If I understand correctly, your network is hanging off of F0/0, your current Internet connection is off of the 4 serials, but you have a new internet connection on F0/1 (metro ethernet or SDSL or something), and you want to route based on the source IP of the traffic, not the destination.
something like this


IIRC, what you need is policy routing. Basically you'll create a route-map that says something like "match access-list 101" (acl 101 will define traffic from 66.236.106.66/224 to anywhere) and then it will "set next hop" or "set interface". Then I think you'll have a second policy that is either empty or says match all which will catch the rest of the traffic and allow it to go the normal route.

I think this may help http://cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009481d.shtml

If you need anything else or any assistance just let me know. If I don't have a complete understanding of what you are trying to do let me know.8