[lug] transparent image background

[D. Stimits]

For all the gimp experts out there, I'm trying to find a way to work
with transparent backgrounds within images, for web pages. The gimp
apparently has a means of doing this, although file formats supporting
it are limited. One such supporting format is gif, but unfortunately, it
is among the evil commercial doo-hickeys, the doo-hickey class being one
that the gimp chose to no longer support export of, for legal reasons.

Can anyone tell me, is there a way with Gimp, or some other linux
package, to take an image that has a pure black background, and
something like a logo on it, and make that pure black background a
transparency that won't block out web page backgrounds that it sits
over? What file format would I use?

Thanks!
D. Stimits, stimits at idcomm.com