51-L (Challenger '86) and STS-107 (Columbia '03) are two out of 113 missions. To dwell on the two that failed out of over a hundred that succeeded is incredibly shallow of us. Sorry. And I'm usually the "glass is half empty" type.
My heart has always belonged to the OV-105, the Endeavour. The Endeavour's next mission is STS-115 (no mission specs yet) and was scheduled to launch May 23, 2003 (not sure what's going to happen now that OV-102 has gone down). Its crew consists of Mission Specialist, Dr. Steven MacLean, from the Canadian Space Agency. [Only Buddy-Girl-K will understand the "Endeavour" and "Stevie Mac" references here =D]
I'm hoping that they learn from STS-107 so that future missions have a better chance of succeeding.
This also means that they'll build a new orbiter soon, which would make it OV-106. I wonder what they're going to christen the OV-106... I vote for "Excelsior". =)