It depends on your BIOS. If your BIOS allows it then you can do it. That is how
I install most Linux. I use a utility called Unebootin that writes an ISO to a
usb key. You need the program, an ISO and a usb key and the locations of each
(ISO and key). Installing doesn't come easier than this. It takes a couple of
minutes to write the ISO to the key versus considerably longer to burn a CD.

You need to either set your BIOS to use usb as the first boot device or have a
way to use a key press to get into a boot menu. Mine is ESC from first boot
screen.

Isn't it unetbootin
http://unetbootin.sourceforge.net/

Wish i'd seen this earlier. Does save on burning a CD - i'm just going
to keep a memstick for releases now. [If it works ok!]. I try and read
a fair bit on the ubuntuforum but it is so large and postings non
stop.

I've just installed unetbootin on 8.04 - seems to work fine.

Assuming it's been available for sometime i do wonder why ubuntu
haven't incorporated such until ver 8.10. I imagine the 8.10 app is
similar to unetbootin.

Doesn't seem to make sense to me. I've been using ubuntu since may 07
ver 6.10 i started with burning CDs for each version. If one can't
bootup on a usb - one has only got to use an older version live CD to
install from the usb. Bearing in mind that a new release could well
need to have more space in future than a CD 700 mb (or there abouts)
why has it taken so long to get round to it.

You are right. My spelling is a typo that slipped through.

Not all distros will work with Unetbootin, but most will. I am not sure why this
is the case.

You can install it as an application or decompress the tar and make the
Unetbootin file executable. It is small enough that you can use it as it is.

Unetbootin allows you to use a pre-downloaded ISO or to download one from a
list. This second option obviously takes longer and if you have the ISO (I
collect them) then it is the way to go. It takes only a minute or two to re-use
the usb key. It is advisable to delete the files on the usb key before you
launch Unetbootin as there is no built in formatting tool and it will overwrite
files with the same name. Otherwise write around them which can make your key
shrink in size over time as not all files are the same and files not
over-written will simply stay on the key until you remove them. Also you need to
mount the key before you launch Unetbootin or your key will not be available.

It is a very handy tool and the first thing that I go to when installing a new
distro. Also saving ISOs is very handy as opposed to cluttering your space with
CDs or DVDs. It gets my vote as the best utility for its simplicity and ease of
use. I have a box of bootable CDs and DVDs of Linux distros which goes back 7 or
8 years. There are dozens of spindles. I don't know what to do with them. They
are too good for landfill and a waste of space in my basement. Someday I will
install Mandrake 7 or Fedora Core 1, just to see what it was like.

Thanks for your comments... but i still don't understand "why has it
taken so long to get round to it." (linux iso to usb that is). For the
last 2/3 yrs all iso could have been saved to usb. Most folk only use
their iso once for installing and that's it until the next version -
that's what i'll be doing from now on.

It has been around, but it hasn't been in wide usage. Unetbootin isn't new. Now
it is getting wider distribution and support and before it there were similar
tools, even from Windows. There is a whole website devoted to it called
PendriveLinux.com. Some distros such as SimplyMEPIS have had the usb key thing
working for years and I think that PCLOS has included it since 2007.

As to why it isn't more common it is a mystery to me because as you say it is
the best way to go, both as a time saver and as a space saver. The idea behind
doing it from the desktop is a little different from Unetbootin's, although in
practice they amount to the same thing. When one creates a usb key from Ubuntu
and other distros it is with the object of taking a copy of the OS with you
wherever you go. Persistence is built in, meaning that you can install
applications and make changes and they will remain (unlike a CD which is not
writable). It is simply a way to take your favourite OS with you and boot it
from any computer.

This can be done with Unetbootin, but it takes a bit of work to make it
persistent as you have to setup the loop device which will be mounted so changes
can be saved. I tend to use Unetbootin simply to install a distro from because
it is quick and dirty. I carried my Ubuntu around on usb key years ago, but I
never had much opportunity to use it, so I stopped.

You can make a bootable USB stick directly from the live CD, just choose
that option after it boots up, make it persistent too.

I'd agree you can make a bootable memstick from the liveCD [since days
of Dapper] but we were discussing how to make a bootable iso from a
memstick. In future i just want to download the new version to
memstick to save on CD burning. After all it only gets used once...
maybe a second time if a glitch.