Writing up this list made me acutely and embarrassingly aware of my shortcomings in describing games.
Had to redo it all over and substitute my ..descriptions.. with their own words in quotation marks.
Tales of Maj'Eyal - "free, open source roguelike RPG, featuring tactical turn-based combat and advanced character building."
One Finger Death Punch - "cinematic kung-fu battles in the fastest, most intense brawler the indie world has ever seen!" (Check out TotalBiscuit's WTF on it)
Transcendence - "Space Combat and Exploration in a Vast and Dangerous Galaxy"
Smugglers 3/4/5 - "turn-based science-fiction space trading game series."
<link=http://www.soldak.com/Drox-Operative/Overview.html>Drox Operative - "starship action RPG with warring alien races, fierce space battles, a dynamic, evolving galaxy, and co-op multiplayer"
Craft the World - "sandbox strategy game, the mix of Dungeon Keeper, Terraria and Dwarf Fortress."
Salt - "Salt is a game based around exploration and adventure where you sail across a vast ocean exploring different islands."
<spoiler=Public Alpha/Beta>
Gnomoria - "sandbox village management game"
Darkout - Think Terraria with better graphics and putting emphasis on lights vs darkness.
Rimworld - "A sci fi colony sim driven by an intelligent AI storyteller."
Wayward - "turn-based, top-down, wilderness survival roguelike"
<spoiler=Keeping an eye on>
Interstellaria - "2d space SIM/RPG/Sandbox game" (Etalyx got a good vid on youtube)
M.O.R.E - "Space strategy M.O.R.E. - Military, Organization, Research, Exploration"
Predestination - "turn-based space 4X game"
<link=http://www.moddb.com/games/stars-of-icarus>Stars of Icarus - "top-down Space-Shooter for Adobe Flash, focused on a deep combat system and exploration, featuring RPG elements."
VoidExpanse - "Science Fiction, top-down action roleplaying game set in outer space."
Out There - "hard sci-fi space exploration game blending roguelike, resource management and gamebook mechanics."
Unclaimed World - "hard sci-fi, colony sim game about survival and exploration of an alien planet."
Drifter - "sandbox space trading game".
Dwell - "multiplayer sandbox MMORPG"
<link=https://www.kickstarter.com/projects/fugitivegames/into-the-stars>Into the Stars - "A single player open-world journey through a distant solar system. Scavenge resources, manage your ship and lead your crew in combat."
Now, some of these might be in the wrong category, a bit old or even seemingly vapourware..
It's hard to keep track. Take Notice.