Lift Pass
Kitzbühel lift passes can be bought at the cable car stations.
For guests arriving in Kitzbühel early in the day on the 24th December you would be best advised to buy your passes right away as there is likely to be a queue on Christmas morning. 
If you plan to ski every day the cheapest way to buy your lift pass is to go for a 6 day consecutive pass for €210.50. If you fancy a day off in the middle or your not planning to ski on the morning of the wedding you could go for a 5 in 7 random use pass for €199, which means you can pick any 5 days in a 7 day period in which to use your pass. If you are unsure how much skiing you want to do there are lots of alternatives from hourly rates, day rates, after 11pm rates, after 2pm rates - it's endless. Browse the ski lift brochure to work out what would be best for you.
For skiers looking to venture out of the Kitzbühel ski area you can purchase the Kitzbühel Alps AllStarCard which covers 7 areas around Tirol and Salzburg including Kitzbühel which costs €224 for 6 days. However Kitzbühel itself has 60 groomed ski runs covering 170km of piste and is served by 54 lifts which for most people will be plenty enough skiing for a week.
Ski and Snowboard hire
It is about 20% cheaper to book equipment via the internet before you go away.
For skis and boots you will probably pay between €100 and €180 for 6 days depending on the quality of the skis you choose.
Here are a couple of sites with discounts on ski hire in the centre of Kitzbühel.
www.alpinresorts.com offer 20%+ discount at Sport 2000 shops. (Be sure to enter promotion code news101 to get the maximum discount)
www.snowrental.net offer 20%+ discount at Element3 Sport Noichl. (The equipment here is a few euros more expensive, but comes with a reccommendation from our wedding planner (Enter code 'HELLOSNOW11' for a further 10% off [Thanks Rob]).
For first time skiers looking to have 5 days of lessons, Crystal Ski have a tuition and equipment deal available for £183 which sounds reasonable. If you are interested we can provide more details.
Piste Maps
View interactive map (click 'winter' bottom right)
Lessons
There is a good choice of ski schools in Kitzbühel providing both group lessons and private lessons.
In Austria most group sessions are for 4 hours a day; 2 hours in the morning; 2 hours in the afternoon.
Not all of the ski schools expect you to book for a full week of lessons, click on the links for more details.
Element3 are well located in the centre of Kitzbühel and offer group lessons for up to 8 people. If you book through Alpin Resorts, they offer a 5% discount on Element3 lessons. They also appear to be basing their prices on junior rates - We're not sure if this is intentional, so it might be worth booking before someone realises :) Alpin Resorts also advertise the group sizes as being between 8 - 10 people, which contradicts with Element3's website?
(The cost is currently €171 for 6 days, 4 hours a day, you can choose fewer days, but they should be consecutive) UPDATE 29/11/2011 - well done if you got on this offer prices are now
€242 for 6 days.
Black Sheep Ski are an English speaking company who have no office in Kitzbühel so you have to book in advance. They offer group lessons for beginners comprising of 2 hours a day for 5 days, Sun - Thurs, costing €100, Max group size 6. Private lessons are available too.
The main ski school in Kitzbühel is Rote Teufel (which translates as Red Devils). They run sessions for all standards in groups of 10-15 people. You do not need to book lessons in advance just turn up on the day and they will allocate you to a group. Beginners must start on a Sunday or Monday. Intermediate and advanced skiers can join on any day of the week. The cost is €180 for 6 days.
If you are unable to find suitable lessons using the above ski schools, here are 2 more which are based in villages surrounding Kitzbühel and accessible using the ski bus. They advertise very similar prices to the previous schools.
Jochberg Ski School
Reith Ski School