Spotter: available for range land units. First rank adds 1 Sight, second allows the unit to see over obstacles.
Radar: available after researching the eponymous technology, allows ships to see past obstacles.
Infiltrator: upgrade for Scouts. First rank allows for passing impassable terrain, second rank allows the unit to enter other people's ZoC, third rank makes you invisible, but prevents the unit from capturing cities.
Route March: available for all military Land units (except Scouts.) First rank gives +2 movement while in friendly territory, the second gives +1 move anywhere that isn't enemy territory, and the third rank gives one extra move in foreign tiles.
Collateral Damage: available for Seige units, bombers, and ranged naval units. Unit kills tile improvements when you attack with it.
Speed Loaders: Gunpowder units only, adds one extra attack.
Air Mobile: only available after discovering Flight. Allows land units to paradrop at increasing ranges.
Marine Training: only available for non-seige ranged land units. First rank allows them to attack while embarked, the second restores their vision as well.