QuickTime
The fastest and most advanced playback software for
panoramas and movies in general has been QuickTime; for at
least one decade. Built to accommodate the onslaught of
data compression technologies and advancements. Apple's
QuickTime file format was chosen by the the International
Standards Organization as the basis for the MPEG 4 file
format. Long recognized for it's great backwards
compatibility and forward thinking.
Java
Java is another means to view panoramas. A bit more
CPU intensive and not quite as smooth, but a decent means
for someone on a modem or without QuickTime.