.
Wow! Who would have thought that there
are so many Gimp users.
I also use Gimp but there are other free
programs out there. I have used a program
called "Paint.net" it's open source but unlike
gimp that has a user interface that seems
to have been invented by martians the ".net"
interface is much like what you'd see with
photo shop.
There has been another thread with this
subject. Maybe if you looked/searched
for it you will be able to find it. As I recall
some people were using power point to
do captions so I guess the lesmister here
is that your ideas are more important than
than your tools.
I did a few posts about editing images and
it's at
URL.
Good luck.