RRDtool is the OpenSource industry standard, high performance data logging and graphing system for time series data. Use it to write your custom monitoring shell scripts or create whole applications using its Perl, Python, Ruby, TCL or PHP bindings.
Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. Automatic graph drawing has many important applications in software engineering, database and web design, networking, and in visual interfaces for many other domains.
Gnuplot is a portable command-line driven graphing utility for linux, OS/2, MS Windows, OSX, VMS, and many other platforms.
Gnuplot supports many types of plots in either 2D and 3D. It can draw using lines, points, boxes, contours, vector fields, surfaces, and various associated text. It also supports various specialized plot types.
Gnuplot supports many different types of output: interactive screen terminals (with mouse and hotkey input), direct output to pen plotters or modern printers, and output to many file formats (eps, fig, jpeg, LaTeX, metafont, pbm, pdf, png, postscript, svg, ...).