I had so much fun reading and contributing to Orion's Arm when it first started. It still has some of the best SF world building I've ever enjoyed. I'd love to see more wide-open shared world fiction out there. SCP is a great example too as gary_0 pointed out.
Been a fan of this for many years. Its likely the source of my fascination with "active structures" from reading far too much about "dynamic compression members".
I really thought it would be cool to build a small scale prototype before I looked at the physics more closely and realised how genuinely hard it is to build the turnaround magnets whatever else you use to bend the "mass stream" back around to the other direction. Still think its cool, but I realised its way beyond what I can possibly build myself with some ball bearings, magnets, and capacitors and electronics like the guys making coilguns use... its way more difficult than that haha.
I wish the Internet was exclusively this sort of thing. You know, dork stuff.
The other examples of this kind of community worldbuilding I can think of are the SCP Foundation[0] and The Elemenstor Saga[1], although I suspect there may be many others out there in the imaginary digital multiverse.
I really enjoy Orion's Arm! There's a substantial variation in quality depending on who is writing and how much investment's been put into a given corner of the site.
I appreciate its outlook a lot, overall - that the future involves change, but not necessarily destruction. It's much more hopeful than a lot of science-fiction tends to be now.
Yeah. I draw the line at magnetic monopoles, which are hypothetical (and it's not looking good for GUTs at the moment), but they are infinitely less bullshit than tachyons and such.
Wormholes and reactionless propulsion are too much for me. It's a cute idea, but I don't believe wormholes exist outside homework problems for students of GR.
Magnetic monopoles are indeed speculative, but at least the theoretical foundations are pretty sound. Dirac predicted them after all, and they play nice with quantum mechanics. Wormholes and the like are where you get really wild problems like time-travel, which you have to arbitrarily prevent via more speculative physics.
The usual argument is that the goal is to write fiction, and you need some plot device to cause interactions, or the end result ends up too boring (for the kind of fiction desired).
Consider trying to make a procedural cop show where each investigation takes 2+ months, and the trial takes place a year later.