Admiral Shelby - Riker wasn't a fan of her in 'The Best Of Both Worlds' and she was the tactical specialist brought onto the Enterprise D to counteract the Borg threat
Transwarp Hubs - Seven mentioned in a Voyager episode that the Borg had I think five of these...so maybe only four left?
Fleet Network - a Borg idea and the ships when linked / taken over seem to arrange themselves in the shape of the Borg language / sign I think
Transporters - clever use of the JLP DNA being added by the Changelings to each ship and then to each officer through stealth...like an opposite of what the bio filters are supposed to do
End Titles - the on screen displays and Okudagrams gave away future episodes parts as each display is used in an episode (Data's neural battle / Jacks' transmitter signal / Beverley's song?)
Enterprise D - the brighter nacelles when it goes to warp
...and yes it can be operated by only a few people (sure it was mentioned in an episode) - but Beverley asks the computer in TNG episode 'Remember Me' when everyone disappears that with a ship this size why would I be the only crew member?
Picard: it cannot be salvaged - well give Geordi 20 years and he'll get it backup and running...