7.8km for Spirit, 19.3km (ongoing) for Opportunity.
It's worth remembering that Lunokhod was not an autonomous vehicle. With the exception of some tilt sensors, it was driven remotely from a control centre in the Crimea - the 2 second delay was just about bearable for its drivers.
One of the purposes of the Lunokhods was to place accurate laser reflectors on the Moon that would be used to measure changes in the distance to the Moon as its orbit continues to spiral outwards. Lunokhod 1's reflector apparently worked for a while but hasn't been seen for a very long time. If anyone is interested, Number 1 lasted 11 months, but only went 10km.
One correction to the original article. The Soviets used Lunar Orbiter photos for navigation and landing site identification, not Apollo.