I love card kits! For the newer stamper, they are great because you get the supplies you need to make cards without having to figure out what to order and without having a bunch of supplies left over when you're done. For the experienced stamper, they are great for when you need a card in a hurry or when you feel like crafting but don't have that creative vibe going to come up with your own designs.
There are several card kits on the retiring list. One of my favorites is the Everyday Occasions Kit. Everything you need (except adhesive) to make 20 cards for assorted occasions. It even includes 2 Stampin' Spots (mini ink pads) and a 7 piece stamp set! Click the link to see all the cards you can make with this kit.
There are also kits like the Greeting You Simply Created Kit. It has the consumable supplies. You provide your own adhesive and ink and then either write your greeting or get the coordinating stamp set (or use one you already have). This kit and its coordinating stamp set, Hey You (clear mount), are not only on the retirement list - they are discounted! (Note: wood mount is retiring, too, but it's not discounted.)
There are other kits on the retirement list - some half off! - and kits that aren't retiring. Check them out!
And just for fun, here's a video highlighting other ideas for the Greeting You kit. This kit is one that's half off. Why not get one to make cards with and one for other projects?