I'm not actually sure if it's linux, but it's GPL: http://www.cgsecurity.org/wiki/TestDisk - TestDisk is supposed to be good at finding lost partions and even converting dynamic to basic for Windows. It can also be run from inside windows to make a text file export of the partition tables.
http://www.demolinux.org/ - This distro is aimed at making a desktop demo of linux. It looks interesting. X, Gnome or KDE.
Hiren's is not strictly Linux. Various antivirus, antimalware, lost password, etc tools: http://www.hiren.info/pages/bootcd
Update: Knoppix is really good. It's an excellent CD to keep handy - the unofficial site for knoppix is here: http://www.knoppix.net/. They've got a good forum and tutorials (and links to download locations, of course). Pop it into any PC that boots from CD, and chances are good that it'll boot without writing anything to your hard drive. Very, very slick. Excellent for the techies toolkit. Get it today! Update 2: http://www.bytebot.net/geekdocs/debian-knoppix.html Some instructions on setting up a debian installation using a Knoppix bootable CD.
This new distro sounds pretty good. Debian + Stuff. It sounds like it's less specifically tuned to live CDs than, say, Knoppix. http://www.mepis.org/
Another live cd: http://www.pclinuxonline.com/pclos/download.html
PC Linux Online's biggest strength is that it aims to provide what users want (i.e. something that "just works") - for me, it works great because it automatically detected my sound and video (integrated Via KM266 chipset) which no other Live CD that I've tried has been able to accomplish. Apparently it has drivers for Nvidia and ATI available too.
A really long list of bootable Linux CD's: http://www.frozentech.com/content/livecd.php?sort=&showonly=
Not technically a live CD, rather a packaged Cygwin+X so that you can run X apps over a network, and get a big collection of GNU tools w/o installing stuff in Windows:
http://xlivecd.indiana.edu/
Site that specializes is Linux distributions that you can install to a USB Flash drive. Very cool. - http://www.pendrivelinux.com