Short answer: Space stations have been refueled on orbit, as well as some small demonstration missions.
There is only a limited number of objects that this is even an option. There are 3 types of docking which have generally happened. Those involving manned spacecraft but not a space station, those involving a space station, and those with unmanned spacecraft. In the first category there are the following missions that I'm aware of.
- Gemini 8/ Agena- No fuel transfer attempted.
- Soyuz/ Soyuz- No fuel transfer attempted. This type was tried early on.
- Apollo/LEM- No fuel transfer attempted.
- Apollo/ Soyuz- No fuel transfer attempted.
- Hubble Space Telescope- Has no propulsion, thus no refueling was possible.
- Other Shuttle satellite servicing missions- I have found a few other missions, but none with fuel transfers.
As for space station dockings, here's a list of all of the space stations that have existed:
- Salyut stations- Contained an engine. The first 4 had no means of refueling, however, Salyut 6 and 7 was refueled on orbit.
- Skylab- Would have been possible to refuel via an EVA, but this doesn't seem to have been done.
- Mir- Frequently refueled by Progress spacecraft.
- International Space Station (ISS)- Frequently refueled
In addition, a few tests have been done with unmanned spacecraft to demonstrate refueling. One of these was done on the ISS (Robotic Refueling Mission), which demonstrates how to fuel with a spacecraft not designed to be refueled. The other is the Orbital Express mission, sponsored by the US government to demonstrate such refueling capacity, which refueled using purposely build spacecraft on orbit.
There are plans for two additional spacecraft to assist with refueling other spacecraft, namely: