For most connections 250K files should be good demo, files > 8meg will fail without an error message due to my PHP config, larger files work if you have PHP setup to work with larger files.
This code has been tested on Firefox 1.5, but should work on any modern browser if you find any bugs post them on the blog or the wiki
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Read the blog posting about it (This relates to the older version but has comments about the new as well)
This demo now uses the php 5.2.0 => uploadprogress extension