Windows Server OS (2003, 2008,2012)

Installing, configuring
Installing/administration domain & network services (AD, GP, DNS, DHCP, Proxy, HTTP(S), FTP, MAIL(Kerio, MDaemon, MS Exchange), MySQL, MSSQL, Samba, WINS, Firewall (Kerio), Terminal Server, RemoteApp, IP-telephony(3СХ))

Unix/Linux:

Client OS (Ubuntu, Fedora, CentOS etc)

Installation, configuration

Server OS (FreeBSD, Ubuntu server, CentOS, Elastix etc)

Installing, configuring, support already configured systems and their optimization
Deploying Network Services:

WEB (Apache, Nginx, THTTPD, Lighttp)
Firewall (IPFW, PF, Iptables)
Mail+Webmail (Kerio,)
FTP (anonymous & with user access)
Samba (share & secure; automatic backups from client machines; PDC powered by Samba)
Monitoring Systems ( Zabbix,)
HelpDesk (GLPI+OCS Inventory, SysAid)
DHCP (open & secure)
VPN (MPD, OpenVPN)
Proxy (Squid, 3proxy, OOPS) + Lightsquid/SARG (Web-resource visitor statistics)
VoIP (Asterisk, Elastix)
Jabber-server (Ejabberd + PGP-encryption)
CVS (git, subversion)