I don't know of any digital camera that will let you write to the memory card when it is in the camera.
You need a card reader/writer.
I have a Canon S2 IS. To get my pictures from the camera to my PC, I just connect the USB cable and copy/paste. But for Christmas, I received a digital picture frame, the kind you can plug a memory card into and show multiple digital photos.
I would like to be able to choose our best 10-12 photos, copy them to a small memory card, and plug it into the digital frame. I assumed I would be able to plug this small memory card into my camera, then copy and paste the photos from the PC on to the memory card - basically the reverse of what I do to get the photos on to my PC.
But for some reason, it won't let me do this. Any ideas on how I can get around it? I really don't have much of a need to purchase a card reader, so I'd like to avoid that if possible. Thanks.