Linux systeminstallation, administration and scripting,
-> bash,perl,python ... etc,
Webserver and application installation and administration,
-> apache, nginx, mysql, postgresql ... etc.
Webpage development and administration
-> html,css,php,javascript, wordpress,joomla,drupal ... etc,
Data mining, data extraction, data analyses, web scrapping,
-> php,python,curl,selenium webdriver ... etc,
CryptoCurrency/CryptoCoin/CryptoMining
-> Blockchain/Bitcoin/Ethereum,
-> setup/amdministrate/support miner (sha256, Scrypt, X11)
-> ASIC/CPU/GPU mining.