_Various_
https://github.com/jaydenmilne/steamsync
https://playnite.link/
https://es.isthereanydeal.com/
https://steam-backlog.com
https://gist.github.com/davispuh/6600880
https://developer.valvesoftware.com/wiki/Steam_browser_protocol
https://completionist.me/
https://www.whenisthenextsteamsale.com/
http://www.lorenzostanco.com/lab/steam/
http://www.enhancedsteam.com/
http://steam.tools/
http://steamsignature.com/
http://astats.astats.nl/astats/
http://www.mysteamgauge.com/
http://www.steamcardexchange.net/
https://test-steamproxy.haloskins.io/tradeoffer/new/?partner=83905207&token=tEx7-bXd
https://giftoff.com/gift-cards/steam-wallet
http://steamrep.com/
http://steamstat.us/
http://steamcharts.com/
http://steamdb.info/
http://www.makeuseof.com/tag/6-tools-for-getting-more-out-of-steam-games/
_Client tweaks_
http://steambanners.booru.org/
https://github.com/rallion/depressurizer
http://test-steamproxy.haloskins.io/groups/pixelvisionskin
( My categories: http://imgur.com/4U1wWoG )
_Giveaways_
https://freebies.indiegala.com/
https://www.indiegala.com/giveaways
http://www.steamgifts.com/
http://steamcompanion.com/
_Bundles_
https://www.humblebundle.com/
https://www.fanatical.com/
https://www.indiegala.com/
http://groupees.com/
_Controls & Game server_
http://www.gameranger.com/
http://joytokey.net/en/
https://github.com/Codeusa/Borderless-Gaming
http://www.highrez.co.uk/downloads/XMouseButtonControl.htm
http://vba-m.com/forum/Thread-xbcd-0-2-7-release-info-updates-will-be-posted-here
https://alia5.github.io/GloSC/
https://github.com/WombatFromHell/OriginSteamOverlayLauncher
_Steam Roulette_
http://thewheelhaus.com/usergames.php
http://steamadvisor.com/advise
http://whatshouldiplayonsteam.com/
http://steam-tools.net/multiplayerroulett/