I have two servers at home, the first one is a Raspberry Pi 3 revision B single board computer and the second one is a laptop.
I use the laptop as a file server, an internet-radio, a torrent seedbox, an I2P router, Team Speak 3 and games server. Raspberry Pi is running an e-mail, a DNS, a HTTP, a XMPP, Mumble, MariaDB, OpenVPN and Tor servers.
Laptop is Acer Packard Bell TE69CX that has Intel Pentium 2117U 1.8GHz 2 cores processor and 4GiB DDR3, system disk and external one are 500GB each.
Services that are available for everyone.
Its metrics you can see here. I set it to use 8 MBits of my Internet connection. It cannot became a guard node because of dynamic IP-address that changes every 10 days.
I run it occasionaly. Nuff said.
I use Liquidsoap and Icecast. I just broadcast almost everything I have.
I use vsftpd. It serves a public share with anonymous access.
Services that are available for a narrow circle of people.
I run it using a classical combination of Postfix, Dovecot (w/Sieve), Spamassassin and OpenDKIM. There's also a web client using Roundcube.
Here's the link.
It's private, but you can join a guest room where you can only write messages. You must use a certificate in order to connect. I don't go there, because it is hard to convince someone to use one more program (and I fully understand that).
Here's the direct link.
I run it using Prosody. It has HTTPS upload service and supports vCard 4. It's a private server where only I can register new users, for security's sake.
Here's the direct link.
I run it as an alternative to Mumble. Restrictions are the same as for Mumble. At least it is not abandoned.
You can get a client here. Server is already in servers.dat file.
I run a pirate Minecraft 1.12.2 server on a laptop for myself and my friends occasionaly. A server named Mandy-Kurgan after a song "Шайтан-арба" of Infernal FuckЪ band. It may also work under Linux but no libs included and not tested.
Services that maintains other services or used exclusively by me.
It's NGiNX and PHP 7. I host this site, startpage for browser and web-clients for DB and mail on it and it also serves as a proxy for internet-radio.
At the moment I run MariaDB. I use it to learn and to handle databases for some of my services.
I started it in an educational purpose to learn more about DNS. Now it serves a DNS cache and domain zone for my LAN, and OpenNIC. It is encrypted using DNSCrypt-proxy.
I run OpenVPN server, so I have an access to my files and inner services from the outside.
For a convenient access to my files.
Transmission just werks.
CUPS with CCP.