Venus [Wiki Link] is one of our closest planets in our own solar system. It size is almost the same as Earth. But the atmosphere is not the same. As it is 400C and mostly made out of sulphuric acid (clouds are made out of this) and carbon dioxide.
According to studies about 80% of Venus surface is covered with volcanoes and volcano lavas. But it is unknown at this time if any of them are active today. But recent observations suggests that there might be active volcanoes on Venus. Most or all volcanoes on Venus are believed to be shield volcano. Rather then any other type of volcano. I do not know if that has changed with more research into Venus during the last few years.
So far about 1600 volcanoes have been identified on Venus. But it is currently unknown at this time if any of them are active or not. But at the moment they are assumed to be extinct. But it is close to impossible to monitor any activity that might exist on Venus. But that it is a good distance from Earth, and the atmosphere does not allow for any monitoring equipment to be installed on the surface of Venus. As any such hardware would just melt in matter of minuets. So for now, what we can see is the only option. Sadly, it is not a whole lot that can be seen on Venus due to extreme cloud cover.
But few years ago a white spot in the clouds of Venus suggested (at least that was the idea) that a volcano eruption had taken place. But it was never proofed far as I know at the time or at later date.
For the moment we know that there where volcanoes on Venus that even made large lava flows. They might even be active volcanoes on Venus today. But proof of that is limited at the moment.
Volcanism on Venus (Wikipedia)
Volcanoes on Venus
Volcanoes on Venus May Still Be Active (Universe Today)
Volcanoes on Venus
Volcanoes on Venus May be Young and Active (Space.com)
Venus Orbiter Finds Potential Active Volcanoes (Wired Science)