System Tools
apt-get, top, cron, crontab, du, df, netstat

Package Manager, Manage Users and Groups, Cron Jobs, Backups, Health Monitor

Web Server
apache, php

Domains, Free SSL Certificates Let's Encrypt, PHP. Custom Applications like RoundCube, WordPress

Email Server
postfix, dovecot, amavis, spamassasin, clamav

Email Accounts, Forwarding, Autoresponder, Queue, AntySpam, AntyVirus, RBL, Backlist, Whitelist, Logs

Databases Management
mysql, mariadb, postgres

MySQL, MariaDB, PostreSQL, Users, Databases, Permissions, Importing, Backups

File Sharing
vsftpd, samba

FTP Server, Samba Server, File Explorer, Home File Server

vsftpd, samba

Fail2Ban, Firewall, VPN, PPTP, Connections Monitoring

Version Control Tools
subversion, git

Subversion - SVN, GIT, Management Users and Groups, Repositories