This is a frame made from an old tablet PC
http://webpages.charter.net/bbiggers/DCExperiments/html/digital_frame.html
This artsy and highly digital-looking picture frame is made from an old 233 Mhz PC laptop running FreeBSD 4.8.
http://www.23degrees.net/tools/archives/56-Making-a-digital-picture-frame.html
the 1400 series what ideal for it's small logic-board and nice screen.
http://www.applefritter.com/node/4971/
This digital frame uses a SmartMedia card to store pictures and CompactFlash card to store a slim version of OS 8, elimating the need for a hard drive.
http://www.macmod.com/content/view/80/
the Powerbook 1400c would be the best.
http://barr104.spymac.com/index.htm
A fancy digital photo frame running OS X with wireless internet, audio(!), and a usable cd drive.
http://home.pacbell.net/sdj544/iframe/
A cheap way to make a frame without a PC.
http://www.mjbok.com/frame/
the steps to create your own digital picture frame from a junk laptop
http://www.aguntherphotography.com/projects/dpvf.htm
I took apart my old, broken iBook and created this digital picture frame with wireless network connectivity.
http://public.fotki.com/Timen/summer_break_2004/iframe/
Step by step documentation of a conversion from Thinkpad 560 into a simple (and cute) digital picture frame.
http://81.5.185.34/tc-one-thousand/others.html#PictureFrame