We see the Sliders briefly return to their home world in Exodus I/II. Is this the only example of the Sliders visiting the same world twice?
Yes, they return to Earth Prime, the dimension of their origin several times across the series. Earth Prime is the Earth that the Sliders originate from, although it is learned in Genesis that Quinn Mallory actually was not born on this earth. The series revolves around the Sliders quest to return to "Earth Prime".
From the Sliders Wikia:
In "Into the Mystic" they encounter Quinn's double who is able to send them home. On their arrival they learn they have only seconds to decide if this is in fact home. The decision rests on a squeaky gate. When it doesn't squeak the Sliders believe that they have not found their home and slide away. (It was Earth Prime, someone oiled the gate.)
Rembrandt and Wade are convinced that the earth they slide into in "Earth Prime" but when it is discovered that this San Francisco has the Azure Gate Bridge instead of the Golden Gate Bridge they realize that they have found Earth Double Prime.
In "The Exodus" while Quinn and Maggie are screening potential Earths, they come across "Earth Prime" but are unable to stay as Maggie is unable to breath its atmosphere.
The third time the Sliders are able to make it home they find that "Earth Prime" has been invaded by the Kromaggs. This spawns a new quest to find a weapon to eject the Kromaggs from their home.
"In The Seer", the series finale, a psychic believes that their next slide, although will return Rembrandt home, will also kill them. This earth has a biological weapon that defeated the Kromaggs, and Rembrandt slides with it but his fate and the fate of "Earth Prime" is unknown.
In addition to the answers already provided, they return once to the world of the 'Exodus' refugees in 'Dinoslide', and also slide away from and back to the 'Prophet' world in Season 4 episode Prophets and Loss:
'Cadmus returns the timer to the Sliders and reveals himself as a mole. The Sliders slide but decide to return so that Samson can carry on the fight.'
Both these instances are thanks to Dr Stephen Jensen's upgrading of the Egyptian Timer in The Exodus.