Handy things to have on your home network

I have some spare computing power laying around on a virtualization server on my LAN, and I was wondering if there is any cool things I can do to enhance my network with that. I already have a local DNS server, several web servers, a media/file server, and several game servers. I would set up a DHCP server, but my dad won't let me disable the router's DHCP, so that's not an option. I can't change any router settings, but I CAN change settings on my laptop (im admin) so is there any cool server software/tools im missing out on? Anything to enhance my network experience? Honestly I'd love to set up a Windows logon server and centralize all of our files onto a NAS, but I have no NAS on which to put them so...plus I don't have $800 to shell out for Windows server.

This software can be Windows or Linux, but not Mac. (if its another free OS thats good too, but I dont own any macs so OSX is out of the question)

Any ideas?

You can apparently use zentyal as a drop in replacement for active directory on windows server, so you can get that centralised authentication without having to buy windows server. I used to use active directory but since moving my file server to linux it's not really useful any more because linux handles file permissions over the network a lot better than windows does.

Plex media server is kind of cool if you want a media server and don't just use network shares to stream the file. 

I can't really think of much else. The best thing to do is think of something that you want to do, like the actual functionality, and then work out the things you'll need to get it to work. 

PfSense Box acting as a VPN server

He won't be able to do anything like that if he can't change the router settings.

He can't turn off dhcp or anything that drastic, but maybe he can forward the port with upnp? Don't have to log in for that.

I suggest just making a FreeBSD VM and playing with it.