If you have GIF file on your computer you can DOWNLOAD (both PC and Mac) my little program to generate a palette.
You can find the download link here at the bottom of the list:
The program are made for me personally so the layout are very simple and it only works perfect with GIF files. It works with jpg and psd also but the are some rgb values changing 1 step up or down so you have to match palette and image by hand. It usually are only one or two colours.
With GIF there are no problems.
Be careful not to have to many colours in your image. I wouln't try images with more than 250 colours.
Hope this will be of help for some.