In its twenty-five-year history, NASA's Space Shuttle program (officially called Space Transportation System or STS), has flown more than one hundred missions. It has enjoyed extraordinary success (such as the building of the International Space Station, and the servicing of the Hubble Space Telescope) but also suffered devastating failures. Two fatal missions (Challenger in 1986 and Columbia in 2003) left fourteen crew members dead. Space Shuttle missions resumed in 2005 with the successful Discovery "Return to Flight" mission.
With animated illustrations explaining each part of the space shuttle, and sidebars summarizing the problems encountered with Columbia and Discovery, Howstuffworks is my pick of the day. It examines the "monumental technology behind America's shuttle program, the mission it was designed to carry out, and the extraordinary efforts that NASA has done to return the shuttle to flight." Best clicks are the interactive graphics that get the reader involved with mousing and clicking.
The NASA History site organizes information from various NASA websites into a single archive. Best bets for students are found in General Information (such as the mission timeline) and Specific Missions. It is the later category (near the bottom of the home page) where you'll find a slide show commemorating the twenty-fifth anniversary of the first Space Shuttle flight on Apr 12, 1981, and links to mini-sites about the horrible Columbia and Challenger accidents.
As I write this, STS-115 (Space Shuttle Atlantis) is on its way to the International Space Station. This site is NASA's Space Shuttle portal, and the best place to visit for information on current and recent missions. Clicks you shouldn't miss include Vehicle Structure (an overview of the Space Shuttle's three main components), NASA TV (video clips of recent launches), and NASA podcasts (subscribe to just one or all five).
Space.com is an online magazine that combines well-written news articles with pop-culture features such as trivia quizzes ("Name that Shuttle!"), computer wallpaper images, and a discussion board. Visit to research previous missions, or to enjoy the amazing photo galleries. In addition to the Space Shuttle section, Space.com covers the solar system, the night sky, and space-related entertainment such as sci-fi movie reviews. Top 10 Alien Abduction Movies, anyone?
Written for middle-school students (and their teachers) by educator Anthony R. Curtis, Space Today Online covers Space Shuttles and related topics such as Astronauts, the Space Station, the Solar System, and Deep Space. I like the fun titles, such as "Poke Around Inside a Space Shuttle" and "Surprise! Astronauts Eat in Orbit (and They Sleep There Too!)" The site is a mix of hosted articles and offsite links, so don't be surprised if you start out at Space Today Online, and end up somewhere else.