Further in towards the Sun from Mercury is Vulcan, a scientific research station located as close as possible to the Sun's surface. It was long postulated that a planet might exist closer to the Sun than Mercury but none was ever found, so Vulcan was constructed. Vulcan uses a great mirror to shield itself from the heat of the Sun. The mirror is also used as a propulsion system for the station to raise or lower it's orbit. Light has energy, and the great light impinging on the mirror of Vulcan can be used for propulsion. Solar sails were proposed as a means of inner system propulsion but Vulcan is the primary user of the technology because the mirror is both necessary as a heat shield and the light is so intense.
The problem of Venus. Atmosphere, tooo much atmosphere. Venus is nearly the same size and mass as Earth. It's day is however slightly longer than it's year, so the Sun would rise in the west, that is if you could stand on the planet and see the sun. But there's the atmosphere. the atmosphere of Venus is composed almost entirely of carbon dioxide and it's pressure is 90 times greater than Earth's. Because of the runaway green house effect of the thick blanket of atmosphere, the surface temperature is about 900 F. Venus is one of the solar system's great challenges to humankind. Because of the lucrative market for carbon in the space colonies however, several corporations have begun operating scoop satellites to mine the atmosphere of Venus. Once most of the atmosphere has been stripped away automated mining systems can begin stripping the planet to it's core. (See "New Earths" by James Oberg)
The inner solar system long neglected by the Earth bound public has proven to be the most important and profitable portion of human Space.