gnuplot FAQ
Using gnuplot
gnuplotting
demo printing values on top of the histogram columns
http://galileo.phys.virginia.edu/compfac/courses/geek-hours/gnuplot.html
loads of complex graph forms (physics)
gnuplot demo index on sourceforge
gantt chart demo
plot of 'sar' output - ibm.com
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 ...