The following page contains a script for creating a bootable clone of the
currently running system on any target media, including thumb drives, flash
drive, or other internal or external bootable media. Naturally, this is most
useful with a keychain thumbdrive.
miniclone is a shell script that either expects to find a volume called "miniclone" or expects to be provided the full path (for example, "/Volumes/miniclone") of a volume it can erase and replace with a minimal installation of Mac OS X from the active boot drive. ONCE AGAIN, MINICLONE WILL IMMEDIATELY ERASE THE CONTENTS OF THE VOLUME YOU AIM IT AT, AND IT WILL NOT CHECK IF THIS IS OKAY. USE AT YOUR OWN RISK.
It is worth noting that Windows XP's GUID support is incomplete at best, and does not totally support multiple partitions on a single drive. In situations where you want to use a multi-partition device, I recommend using an MBR partition table, and rEFIt (link below) to allow Mac OS X to boot off the MBR-partitioned device. Just installing rEFIt is enough; no need to configure it.
In order to run miniclone, either invoke it as root or just type: sudo miniclone /Volumes/target
Replace "target" with the volume name of an already formatted and mounted
partition you want to use. miniclone will figure out its device file, wipe it
clean with a new HFS+ partition, and start replacing it with a subset of the
contents of your boot drive, as specified in the script. Using a text editor,
it's very easy to modify miniclone to add or remove applications, directories,
or services.