Very scalable statistics collection engine with a powerful graphing/visualization UI. Backs off a database similar to RRD.
#chart
MindMeister – Online Mind Mapping
MindMeister – Online Mind Mapping
MindMeister supports all the standard features of a classic mind mapping tool – only online, and with as many simultaneous users as you like!
flot – Google Code
Flot is a pure Javascript plotting library for jQuery. It produces graphical plots of arbitrary datasets on-the-fly client-side.
Google Chart API – Google Code
Google Chart API – Google Code
Surprisingly thorough charting API from Google. Intended to be accessed via JavaScript. Loads of style, color, shading etc options. No sparklines.
LastGraph
Very cool web app that graphs your listening habits on Last.fm as a waveform, containing streaks representing the relative frequency of artists in your listening history.
PHP Sparkline Library Docs
Detailed information (in a wiki) on the usage of the PHP Sparkline library