http://www.mribti.com/barcode/sample.php
http://www.ashberg.de/php-barcode/download/
Script para la libreria FPDF que genera archivos PDF
http://www.fpdf.org/en/script/script5.php
http://www.fpdf.org/en/script/script27.php
http://www.fpdf.org/en/script/script46.php
http://www.fpdf.org/en/script/script67.php
http://www.fpdf.org/en/script/script68.php
http://www.fpdf.org/en/script/script85.php
http://www.fpdf.org/en/script/script88.php
TCPDF es una Libreria PDF para PHP
http://www.tecnick.com/public/code/cp_dpage.php?aiocp_dp=tcpdf_examples
http://www.tecnick.com/pagefiles/tcpdf/example_050.pdf
http://www.tecnick.com/pagefiles/tcpdf/example_027.pdf
QR-code
http://prgm.spipu.net/php_qrcode
http://www.tecnick.com/pagefiles/tcpdf/example_050.pdf
http://megaui.net/fukuchi/works/qrencode/index.en.html
http://www.kornnuts.com/dev/barcode/qrcode.php
http://www.swetake.com/qr/index-e.html
http://www.java4less.com/barcodes/QRCode/php/demo.shtml
http://translate.google.com.ar/translate?hl=es&sl=auto&tl=es&u=http%3A%2F%2Fwww.qrcode.com%2Findex.html
http://code.google.com/p/qrforall/
AztecCode
http://www.java4less.com/barcodes/AztecCode/php/demo.shtml
MaxiCode
http://www.java4less.com/RMaxiCode-php/demo.shtml
RDataMatrix
http://www.java4less.com/RDataMatrix-php/demo.shtml
RPDF417
http://www.java4less.com/RPDF417-php/demo.shtml
BarCodes 1D: "Code-39, Code-39 (Extended), UPCA, UPCE, EAN-8, EAN-13, CODE-128, EAN-128, Code 11, Code-93, Code-93 extended, Industrial 25, Interleaved 2 of 5 , Matrix 25, Postnet, Codabar and MSI"
http://www.java4less.com/barcodes/1D/php/demo.shtml
Existen varias herramientas en la web que nos ayudan a crear códigos de barras a partir de un conjunto de letras y números.