Third Party Boards
From Gumstix User Wiki
iXion is a Gumstix Overo-based, multimedia platform with several features like a 5" LCD touchscreen, HDMI video out, 802.11 b/g (Wifi), Bluetooth, HSDPA, GPS, USB, Ethernet and more.
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The design for the iXion expansion board will be completely open-sourced at here within the next week, so check for that.
A video of the iXion board has been posted on youtube here.
If you have designed a third party board and would like to make other people aware of it, please list it here.