Boson is a realtime strategy game with 3D graphics. Seemingly last updated in 2006, this project must have been quite nice looking for it's time. This is a genre I really appreciate, and there are few free modern-day RTS games, so a revival of this project would be cool. Last code update was in 2008, so perhaps there are already unreleased updates available.
Dark Oberon is another RTS, but with a very unique premise; graphics are made from real modeled plasticine. It looks awesome on screenshots, but I remember when trying it at some time that it felt a bit incomplete. Version history is 1.0 RC2 from late 2006. Perhaps someone could give this game that last stretch it needs?
Thunder & Lightning
Thunder & Lightning is a flight simulator, a type of game I haven't covered on this page yet. And while there are a bunch of excellent open fligh sims, this one has a futuristic touch which I somehow liked. Last news is from 2011, but nothing seems to have happened since then.
Balazar III is a multiplayer dungeon crawler, and that should pretty much be enough of a description to make it sound interesting. :) Rolepaying with friends, be it digital or not, is always fun and I would really like for this project to be continued.
Battle of Antargis
More RTS gaming; you can see I really crave this genre. Battle of Antargis was abandoned 2008 early in development, but it already contained a tutorial and a bit of campaign as well as quite decent graphics. In usual RTS manner you build towns and recruit heroes to fight for you, but an interesting concept in this game is that inhabitants have a mind of their own and you can't control them directly. Would have loved to see this developed more.
These are far from all projects that have met with a similar fate. Expect more lists like this as I go through various interesting projects from over the years!