Microsoft have released a new beta product for Windows Mobile (and also iPhone) called Microsoft Tag
This allows scanning of 2d barcodes with the device camera which can open specific URLs etc. The client software varies slightly depending on the capabilities of your device, on my Samsung Blackjack it offers realtime scanning – you just have to position the code roughly in a rectangular frame on the screen. On a HTC Touch device it invokes the camera capture dialog which is a lot more clunky.
Go to http://gettag.mobi on your device to download the client. You can sign in to the tag.microsoft.com website using a Passport and create new tags yourself. Apparently this will support other 2d barcode types in the future for now it uses HCCB an arrangement of coloured triangles.
The attached PDF contains a generated tag to get you started.