Being able to boot from a USB stick can be very useful – whether to install a new distribution on a netbook, or to have your own portable distribution to carry round with you. Unfortunately, you can't just write an ISO file to a USB stick and have it be bootable, as you can with a CD or DAVE.
It's possible to do the necessary work to resolve this manually; but far and away the easiest way to deal with the problem is to use the usb-creator program available with Ubuntu. Currently it's not directly available as a Debian stable package, but you can grab it from Ubuntu by adding this line (change us to gb if you're U.K.-based) to your /etc/apt/sources.list file:
deb http://us.archive.ubuntu.com/ubuntu/ jaunty main
After saving the file, run apt-get update; apt-get install usb-creator. You may wish to delete this line and run apt-get update again after the program has been installed, to avoid potential future package conflicts.
Once it's installed, mount your USB key and check there's enough space on it for the ISO file. Then run usb-creator, and choose the correct ISO file and drive. Note that it's a graphical program, but it's lightweight and will happily run over an ssh connection. Once the ISO file has been written, you're done.
A particularly useful option, if you want to create a portable distribution, is the ability to use part of the USB stick for writeable storage. This means when you boot off the USB key, it'll use that space to save your files rather than discarding them on shutdown.
Juliet Kemp has been messing around with Linux systems, for financial reward and otherwise, for about a decade. She is also the author of "Linux System Administration Recipes: A Problem-Solution Approach" (Apress, 2009).