I've finally gotten galeon to compile, and there was at least one other person who was having difficulty with it, so I'm posting what I did.
First, there's a new version of Galeon (0.7.2) which goes with Mozilla M17; get it. If you haven't already, download the binary tarball of Mozilla M17 (there doesn't seem to be a debian package of it yet). Extract it in /usr/local and rename the "package" directory it creates to "mozilla" so you'll have it installed in /usr/local/mozilla. (If you want it installed somewhere else, you'll probably need to use the environment variable as directed in Galeon's INSTALL file.) The quick way to get the headers, without having to download the 20MB mozilla source and sit through hours of compiling: download the mozilla development RPM from http://people.redhat.com/blizzard/software/RPMS/i386/mozilla-devel-M17-2.i386.rpm and make it a deb package with alien, then install the new deb with a dpkg -i command. That puts the mozilla headers in /usr/include/mozilla. After that, ./configure (no paramaters needed for configure), make, make install, and it should all work (hopefully). Worked fine for me this time. :) Hope this helps someone. Tom