I love the Farcaster network of the World Web from Dan Simmons’ Hyperion Cantos (for anyone who hasnt read the books, they’re essentially frameless stargates that are always on). Such a cool concept of being able to build a series of them linking the main commercial streets of the biggest cities on different planets together; thus making one gigantic and near endless market across hundreds of worlds… and anyone can just walk from one planet to another across hundreds or thousands of light years.
What I really like about that book series though is that the Farcasters are not the only means of FTL… and that there are sound reasons to use another method over them OR even to oppose your planet getting connected to the Farcaster network. Just seriously good world building.
Funny thing is that, while a similar principle, they’re safer and more ethical than the Star Trek “suicide booth” transporters.