My girlfriend ordered a cheap WonderMedia 8650 based tablet from Deal Extreme.  http://www.dealextreme.com/p/7-touch-screen-lcd-google-android-2-2-tablet-pc-w-wifi-camera-tf-arm-v5-349-79mhz-70053

This device is a nifty IPad ripoff...  It runs Android 2.2 (froyo) and has a little dongle that provides two USB ports and a RJ45 ethernet port.  Rumor has it that there is a serial port inside the box too...  The connector may be compatible with the 24-pin zune one http://techknow.freeforums.org/viewtopic.php?forum_uri=uberoid-wm8650-1-3-hybrid-honeycombmod-v5&t=650&start=460&sid=49774aaf78711a9e3675d305a1b1a84a though I doubt the pinout http://pinouts.ru/PortableDevices/ms_zune_pinout.shtml will match.  Still, I can probably get a connector or 5 from sparkfun http://www.sparkfun.com/products/8608 and wire up accessories to my hearts content.

It has pretty good HID drivers, so I can plug in a small keyboard and mouse and treat it like a normal computer, which is handy, because when I originally tried to upgrade the firmware, I killed the touchscreen driver.  I could still plug in a mouse and confirm that the machine worked though.  I loaded HardCoreHacking's Uberoid  http://techknow.freeforums.org/viewtopic.php?forum_uri=uberoid-wm8650-1-3-0-hybrid-honeycombmod-v6-final&t=801&start=&sid=c9744a30f435c1720b7a7ade7853fe72 version 6 final  firmware and ran changer.bat, and I eventually got the device to boot with firmware option 2.  I have the blue led version of the device, with a black audio jack, a 7" screen and it vibrates on startup.  Unfortunately, the option 2 firmware is for the green led version, which has a different touchscreen chip.  I found instructions here: http://www.mp4nation.net/forum/viewtopic.php?f=73&t=21975&sid=16661bb7a1f4dabca561d797e2ad85cc suggesting that I could modify some config files and write the driver to the SD card.  I edited FirmwareInstall/packages/fs_patch/root_patch/system/default.prop and changed ro.wmt.touchpannel=0 to ro.wmt.touchpannel=1 then I edited FirmwareInstall/env/env_uboot and changed setenv wmt.io.touch 1:vt1603:2:800:480 to setenv wmt.io.touch 1:uor615x:0:800:480 I had to add the line setenv touchcodec vt1603.  Then I had to run changer.bat and type SD to copy the files to the SD card... Do NOT select option 2 again like I did the first time, since that will re-write the config files and undo your changes... So to sum up: you run changer.bat, select 2, say no to the copy and format questions.  Then you hack some config files, then run changer again and select SD to write the actual firmware to the card.  Stick the card in the machine and boot.  It will run throught a bunch of copying steps and prompt you to eject the card.  If you get stuck at the "Uberoid" screen for more than 15 minutes or so, then the option you tried did not work.  I was stuck this way at first, since I first tried option 11, then option 1.  Option 2 did the job for my tablet...

Now some people have taken these things apart.  I have not needed to do so, but in case you do, the front panel is apparently just a sticker. I found a youtube video showing how to get to the 4 screws in the corners... I can't find the link right now, but basically you just stick a thin blade under the edge near the back button and work out to the corners then peel it off.  After that unscrew and lift out the screen.  There are some good pictures of the innards here: http://techknow.freeforums.org/opened-m009s-pictures-t501.html