An interesting question! I'm going to assume that you mean positive
contributions, as Voyager's negative contributions would be a list a mile long.
1. Departing from the Saucer/Nacelle Enterprise style while remaining distictively starfleet.
2. Technical improvements in special effects and on screen displays, notably in astrometrics.
3. Starship planetary landing
4. the Midas Array
5. Further reinforcing the awesome "all good things" future uniform. (too bad Star Trek Online ignored it)