I need a stripped down linux install that will automatically open a web browser and connect to a point of sale server, but it has to run off a static linux live usb. Absolutely no data should be saved on the device. Speed and fast boot times would be a plus, but the hardware this is going on is overpowered for this already, so not really a big deal. The user should not have to touch any interface but the web interface for the POS server. Puppy linux seemed like a good distro to start with, but it doesn't have to be any particular distribution. I don't know how to set up a live usb to do this, and would appreciate any help or suggestions you can give me.

Slitaz is a small live-distribution that can be customized and has the tools for generating a new USB image already installed.
Debian's Live Build would also be worth a try, even more flexible, but a bit more to learn.

SliTaz looks like a good option, but I'll need to remove the boot menu and the configuration on startup. Also, it is having serious problems on my laptop (hangs on boot if ethernet is plugged in, and absolutely no internet connectivity at all).

i think any live-usb (with persitent overlay) should be able to add a line like: to the live users ~/.bash_profile. also do you have a credit card reader... most will work by cat-ing /dev/hiddev0 tree but you will likely need to write a firefox extension to read it (like paypals merchant website extention for internet explorer).

Debian Live Build is well documented
-- a bit to learn
http://live.debian.net/
http://live.debian.net/devel/live-build/
-- manuals --
http://live.debian.net/manual/stable...manual.en.html

but i my opinion documentation is a great start

but any live image can do the job

likely for POS you will want a "persistent" install with an encrypted partition

I've never played with porteus nor know how well it works but it has a kiosk version. It will automatically start firefox and load the homepage and you can use the wizard to build an iso with custom settings.

http://www.porteus.org/