I have a client who wants a new online booking system that works in an iframes so it can be called and run from a range of his websites.
His websites are yet to be built either, I will be doing that.
The business is about driving performance cars on track days, customers have to
create an account,
choose the car they want (should show images and a bit of spec on the cars too)
choose the day and timeslot
pay online or enter coupon code (if Groupon then work with the API to get it verified)
Show receipt and itinary in a printable PDF
Add booking details to Outlook calendar for the customer
For the company, produce a table page that prints in A4 of all the drivers and the cars they will be driving and the times they are booked
Produce for each driver a document that has their details on it (the document will be a waiver and the rules)
Produce for each driver a certificate of completion that is awarded after each driver has done their drive.
As you can see this is a complex system, and will need a CMS at the back to allow for changes to the templates and content for integration.
It will need to be in PHP so we can host it, and ideally WordPress because its my favourite, but thats' not a dealbreaker.