Space is – as Star Trek puts it – the "final frontier". It's still a tiny market by anyone's standard, but commercial space tourism has arrived for those who can afford it.
Driven to prove their superiority during the Cold War, as well as to gain a strategic advantage, the U.S.A. and the U.S.S.R. began a space race during the 1960s. In an astonishingly short time period, the U.S. Apollo program landed human beings on the moon and the Soviet Salyut program kept them in orbit for months at a time. Probes began to explore the solar system. Space seemed very close; at one point tickets to the moon and to as-yet-non-existing space stations were being sold.
After the Space Race ended, a new sense of reality set in. The wild dreams of the 60s and 70s died, and humanity turned its attention Earthward again. Space travel beyond Earth's orbit became the exclusive domain of mankind's robotic explorers, and high-profile tragedies both reaching and returning from orbit provided sobering reminders of the risks of space travel. By the end of the 20th Century, travel into space was still exclusively the domain of governmental organizations.
However, necessity changed the situation with the dawn of the 21st century. Desperate for funds, the Russian space agency began to sell seats on Soyuz launches. Businessman Dennis Tito became the first pay-to-fly space tourist in April 2001, and as of September 2006, three more have followed in his footsteps.
Although physical fitness remains a concern, the main obstacle to reaching space is the depth of your wallet. In increasing order of both cost and distance from the Earth:
While not actual space travel, the weightlessness experienced in orbit can be duplicated (for durations of less than a minute at a time) with a calibrated parabolic aircraft flight, which alternates low g-forces at the heights of its arcs with high g-forces at the bottoms.
Edge of space
Flights at altitudes of less than 100 km do not qualify as true spaceflight, but it is possible to see the curvature of the Earth from altitudes as (comparatively) low as 25 km.
Sub-orbital flight is defined as flight at altitudes higher than 100 km but at speeds insufficient to achieve orbit. While there are currently no operators offering sub-orbital flight, the privately funded and built SpaceShipOne in 2004 demonstrated that this is a possible market and the race is on to commercialize it.
All that sub-orbital stuff is pretty nifty, but these days no one's really ready to accept that you were "in space" until you've been in orbit around the Earth. There's no single altitude for this (it depends on your orbital velocity), but due to atmospheric drag it's only practical above 350 km. Commonly known as Low Earth Orbit, this is currently the exclusive domain of U.S. Space Shuttles, Russian Soyuz vessels, Chinese Shenzhou craft, and the International Space Station. This itinerary is likely the most expensive in the world.
Human travel beyond low Earth orbit has not been done since the cancelation of the U.S. Apollo program in 1972. The only programs actively working to re-establish this capability are governmental in nature. However in 2005, Space Adventures announced its intention to work with Russian spacecraft manufacturer Energia and the Russian space agency to offer a roughly one-week two-passenger flight around the Moon (no orbit, no landing) in a booster-equipped Soyuz craft for US$100 million per person, as early as 2010. This depends on a customer making a hefty deposit to get the project running, so don't wait for them to announce a flight date to get your name in.
Although space food has come a long way in terms of taste and variety in recent decades, the quality and taste is still not up to standards of most connoisseurs of fine cuisine. Due to the high delivery costs, food eaten in space is also some of the most expensive in the world (or rather, out of it).
In 2006, Bigelow Aerospace  successfully tested the first prototype of an inflatable space hotel. However, even if everything goes according to plan, the real thing won't be up in orbit before 2012.
Space is not safe. It's much safer today than it was in the 1960s, but it remains an inherently dangerous environment to put yourself in. Cosmic radiation, extreme temperatures, micrometeorites, engineering mistakes, high speeds, explosive fuels, the distance to terra firma, and the lack of atmosphere make any unplanned situation potentially life threatening.
What goes up, must come down.
At least for now.
Fortunately, there are countless opportunities for exploration and discovery down on the surface, in places such as Africa, Asia, Europe, the Middle East, North, Central, and South Americas, and countless islands in between...