A Serviced Component living inside a COM+ Server Application could be used as an IPC "broker". It'd be always-on, resident in RAM. If anything needed to be persisted, it could be stored in a local XML file or an ISAM table.
Or what about a message queue for IPC? Not as flexible as a SC but you get the storage question answered for free. Maybe a combo of SC+MSMQ for persistent storage. Or if you want to live with the assumption that TCP is always on the computer, install the loopback adapter and give it an internal Class C address (make it non/routable if you want). Since NT4, I've been installing the loopback adapter as part of a server build. It's better to have it and not need it.... It gets away from worrying about what other apps might do with 127.0.0.1. It also lets you run "public" services on the box that you want kept "private". :) As a ferinstance, I needed a centralized way for several Win2K Services living on the same hardware to send mail. I created an SMTP server on the loopback NIC and set it to relay for everyone with no security checks. Since the SMTP server could only listen to network traffic inside the box, mail would only be delivered for my unattended processes on the same server; external hosts can't see that port 25 is open because they can't even reach it. You can read messages from the Advanced DOTNET archive, unsubscribe from Advanced DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
