As per this Wikipedia article there have been a total of 5 orbiters successfully deployed to Venus:
Of which only the Akatsuki seems to be currently operational.
Could it be used to communicate to other potential satellites or for data relay purposes to communicate with Earth (e.g. when a potential new spacecraft is on the far side of Venus)? What would be the approximate bandwidth?
Is there any other usable infrastructure in orbit around Venus? Could it be used for navigational purposes?