Portable background process / service?

[gabars]

Hi, I'm looking for a way to have an interactive shell that would switch to background (it's a server) and keep running but free the console. I need it to work in linux and windows too, cygwin is an option, but I guess that would mean the cygwin terminal would stay open?
I'm using Qt for networking, so sticking to qt or std solutions would be nice. I could make a GUI and put it in the taskbar, but I'd rather stick to a console server for headless computers.

Any ideas?