1. If you are using UKMail you can use the invoice number to provide tracking on couriers own site. There are UKMail views that provide the information to their sites and emails that provide direct links to the customers orders on their websites.
2. You can add custom values to your orders. These can be manually entered into the order and then used in emails. More info. here:
http://www.1stoporders.co.uk/1StopOrdersDefCV.html
3. You can provide online tracking on your website. You can then send an email to the customer to reference this and/or provide online tracking on your own website.
http://www.1stoporders.co.uk/1StopOrdersDefTO.html