http://www.eve-central.com/home/softwarePlease all download that, once installed use the options to point it to the marketlogs folder in your eve section in "my documents". Everytime you view the market for an item, click the "Export to File" button at the bottom of the market window.
The tool will upload the info therein to EVE-Central, which aggregates market info across the cluster. Its not a 100% certain source, but helps find patterns and some good sales areas