I started out with a 2GB SD card, but I'm finding this a bit cosy, so I've bought a 16GB card to replace it. With a single Pi, can I transfer all my work between the cards, or do I need to start from scratch?
You should be able to copy the image, using the same application you flashed it with (or the
dd command in Linux):
dd if=/dev/sdx of=/path/to/image
sdx represents the SD card.
This can then be flashed onto the new SD card just like the original one:
dd if=/path/to/image of=/dev/sdx
For more information, see this question:
And you can see how to increase the size of the image here:
There is an app pre-installed with raspbian that can copy the whole sdcard into a new sdcard through USB. The name of the app is sd card copier. It can be found in accessories.