You might have seen different kinds of barcode printed on different products. That we buy form market. Barcode are used to hide some information. Specific machines are used to decode such barcode. But now you can decode such barcodes with help of your mobile phone.
Example of Barcode:
Example Of Barcode
Barcode Reder Application for Mobile PhoneBarcode Reder Application for Mobile Phone

Compatible devices: S60 3rd Edition, Nokia Nseries, Nokia Eseries.

Here are several link of different Barcode reader applications.