I still use a couple of HP N40Ls for NAS. They’re not fast but they hold up just fine and are as reliable as a brick. The newer models look pretty interesting if you can pick one up used.
The Optiplex micro workstations are also pretty awesome for servers.
Zoneminder is a pretty solid setup for IP security cameras, and the zmninja app is really nice too. I had tried it years ago but got back to it recently with some sketchy IP cameras. I just put them in their own VLAN, no Internet access, Zoneminder does motion detection and event recording, and so far I'm quite pleased with it.
I still use a couple of HP N40Ls for NAS. They’re not fast but they hold up just fine and are as reliable as a brick. The newer models look pretty interesting if you can pick one up used.
The Optiplex micro workstations are also pretty awesome for servers.