richardvm,
I don't think this is a router configuration issue. The router is concerned with network segments and joining the network segments. Whether or not you are a member of a domain or a workgroup is irrelevant. If you can ping the server from a workgroup computer, there is no router adjustment necessary. YOu mention multiple subnets in the post heading but don't mention it in the body. If you can not ping the servers because they are in another subnet, then all you need to do is add a route to the Linksys routing table. Access the router's configuration and go to the Advanced tab. Then select the Static Routing tab. You can add the route there. For specifics on how to do this, look at the Help or post back with the details.
If there is no routing issue or after you've added the route, to allow the workgroup computers to participate in the domain, accounts will have to be added on the Domain Controllers for the users and the computers. Once that is done, you need to go to the workgroup computers and have them "join" the domain. Do this by opening the Network Neighborhood Properties or the Network control panel. There should be a spot where it indicates the domin/workgroup membership. Click the Change button and put the domain in.
Hope that helps.
The Old Man