I love it when i see something so basic and simple that has high value to me.
When you book a car with Avis at the end of your booking you get the option to "Add to Email Calendar". Clicking this will prompt you with a Calendar file (.vcf). Simple open it ... and Outlook will open the calendar item (if you use outlook) .. then you can simply save to your calendar.
VCF files are nothing new ... but it really makes things easier. I would normally have to create a calendar item and copy and paste all my reservation details into that item. This way it is all in there for you. Fantastic.
I stick everything in my calendar so that it syncs with my Windows Mobile SmartPhone ... i forget everything otherwise.
More sites should do this. Airlines! Cinemas! Theaters! ... the list goes on.