Filesaver plug can be used to save images or text files.
<img src="http://dl.dropbox.com/u/22173473/filesaverim.jpg" border="0" />
In the above example: (using MultilineBox plugin also)
1, I used the FileReader plugin to load new image texture for a sprite.
2, Clicking 'save1' button saves the texture as 'PIC.png'
3, Clicking 'save2' button saves the image as 'test.txt' (Base64)