GNUPlot

• Using gnuplot
• gnuplotting
• demo printing values on top of the histogram columns
• [1]loads of complex graph forms (physics)
• gnuplot demo index on sourceforge
• gantt chart demo

Treat x axis as date/time (epoch)

set xdata time
set timefmt "%s"
# set xtics 3600
set format x "%H:%M:%S" # or whatever
plot ...