Well I did a web search looking for "other" internet appliances that are/will/might be on the market. This is what I found. Hopefully, if anyone else has more we can build a list of possible hackable machines.
Here is the list (and where possible a quick comment on each):
http://www.qbenet.com/indexflash.htm : Very cool looking, but VERY expensive... $2000+
http://www.boundless.com/ibrow/ : Same as the virgin webplayer (identical actually), maybe these guys will sell the defunct Virgin stock?
http://www.pc.ibm.com/us/netvista/thinclient.html : No prices listed but I think that this is IBM's response to the ThinkNIC
http://www.screenmedia.no/ : Again cool product, but seems to be vapourware at the moment, has potential though
http://www.thinknic.com/ : What we all know and love.
http://www.qubit.net/flash.html : Again a product with possibilities, but judge for yourself
http://www.trolltouch.com/elite1.html : No comment, judge for yourself
http://www.epods.com/ : Guess they are dead now.
http://www.fic.com.tw/systems/Ia/aqua.asp FIC: Aqua Transmeta 300-400MHz, 7.4" 640x480 LCD, no kb, pen, price unknown : Dead Link Anyone know of a live link?
http://www.neoware.com/neolinux/eon_about.html :Another ThinkNIC type solution?
http://www.portwell.com/Panel.htm : A Hacker in the true sense of the word, however, I don't think there is much activity here at the moment.
Please feel free to add to the list.