Since CF cards are so cheap now — $20 or so, especially with rebates, replacing the old (often noisy) drives in laptops with CF seems a good idea for many applications, not just for a digital photo frame. Old laptops are often found in people’s houses for near-free, and with damn-small linux or even old Win98 they can run just fine on an old CF card for a silent, low-power extra computer for slides, web browsing etc. I just got one myself and will convert an old laptop (I can keep the old HD if I want the old personality back.)

Old laptops only have PCMCIA (not Cardbus) which makes it a little harder to pick up cheap cards for them, but they can be found. If they have USB you’re golden.