Debian 6 live USB flash drive
I got this from different locations and put the pieces together until I came up with the 10 step solution. Note that you need a running Linux in order to perform the given tasks. I don't know about Windows or MacOS. I will only pin down the several steps. I will not explain how to perform the single tasks. These are computer basics and you should know them already, otherwise: Google is your friend.
You should get any debian-6.0*.iso you like as bootable on an USB flash drive with this steps, as long as the flash drive is big enough for the contents of the iso and you know how to transfer the steps for your desired *.iso. I used the live-gnome one.
1. Format your USB flash drive with FAT16
2. Download your favorite debian*.iso via torrent from the debian site.
3. Extract the contents of the debian*.iso to your flash drive (yeah, extract. With an archiv manager or else.)
On your Flash Drive:
4. rename the folder isolinux to syslinux
5. open syslinux and rename isolinux.cfg to syslinux.cfg
6. open syslinux.cfg, stdmenu.cfg and exithelp.cfg in an editor and change any isolinux to syslinux
In a terminal:
8. run install-mbr /dev/sdX just to make sure, the stick has a mbr to boot from (X stands for the letter of your flash drive.)
9. run syslinux /dev/sdX1 to install a simple bootloader
10. create a file syslinux.cfg on your stick and put following lines into it (if you want to start any other kernel than the live one, you may change it):
default live/vmlinuz append initrd=live/initrd.img
Now boot from the stick. When Prompted "MBR FA:" press a, when prompted MBR 1234F: press 1.
Voilá Debian 6.0 Squeeze bootable live (or whatever you used) from a flash drive!