You must forward the NetBIOS broadcasts to the other networks. I think the only way to do that is by bridging the interfaces, so not ideal.
Otherwise, I think it's for the Wintel guys to solve. Certainly a WINS/NetBIOS name server can perform any name resolution, but not sure about the browsing / network discovery element.
Would be interested to know what other members have done. It must be a common enough issue on Campus networks today what with VLAN segmentation being so popular.
Part of the fix appears to be as simple as installing WINS on your DC and configuring all client PCs as WINS clients.
However, for the browsing element, there seems to be another peice of work where each VLAN must have a master browser which updates your domain master browser which holds a list of all the devices.
You also need to ensure the firewall on each client PC is not blocking NetBIOS and file and print sharing is enabled.
Sorry, I can't test it here and not really my area, but would be really useful to know how you get on...
Well if you have the intervlan routing enabled you can simply browse the computers by their IP addresses but if you want to be able to browse them via host names then use the DNS. DNS server can sit on any network out of those 3 really. As long as all computers can access that DNS server and DHCP server is giving out that DNS server(s) to the PC's you should be good to go.