I've started collecting overstock history data, and you can query this for a chart covering the last 24-hour period for any item. There's currently no front-end you can use to select the item you're interested in (I may be adding this) but you can enter the item and quality IDs if you know them. For example, for keys: http://www.chrishowie.com/tf2wh-charts/index.py/?item_id=5021&quality_id=6 Data has 1-minute granularity. If rendering the chart is really slow... get a faster computer. Update: New overstock/price history chart website is at http://tf2wh-charts.chrishowie.com/ -- the URL above will simply redirect here.