(05:23:33 PM) Billiard: CarlFK: you can transfer the alpha channel to
a layer mask to directly modify it
(05:24:53 PM) pgimeno: CarlFK: also, Selection to Alpha allows you to
"select based on transparency"

Don't ask me anything about it - join the #gimp channel.
I can help with IRC.

You can try paint.net. http://getpaint.net

It is not as feature-rich as Photoshop or Gimp, but it is better than MS
Paint, and it is easy to use.  I use it for a lot of icons and simple
drawings.  The magic wand tool can probably do what you want.  Just google
around, you can find lots of tutorials.

--John

When I made games for Gameboy we used a tool called Pro-Motion.  It was
hands down the best pixel editor since it was based on the old school tool
called dpaint..

http://www.cosmigo.com/promotion/index.php

After using Pixelformer, I found it useful for setting pixel values,
including the alpha channel, in one operation, and specifying alpha values
in hexadecimal rather than percentages; however the move, copy, and resize
operations do not appear to work properly, and the export operation does
not store the modified file under the same directory that it was read
from.  I am still using GIMP to move or copy parts of an image, resize or
scale images, and set an entire selected area to the same value
(Pixelformer will only change those pixels that match the one under the
fill cursor).  This requires using two programs to make changes to the same
image.  The "ungradient tool" that I asked about would change all of the
pixels in the image (or a selected area) that have a value in a specified
range to a single value; I still have not found anything to do this.