I store my DVDs in DiscGear-22s, and I devote one side (11 slots) to my Leslies. I usually do them "my" way, i.e. use dumbbells when she doesn't, jog when she doesn't, add my own moves, etc. so I don't care about walks specifically geared for arms or abs or whatever. These are the ones with enough variety (moves, sets, background walkers) and passable music that have made my cut (I like space-saving compilations):
1. Deluxe Walk (older 2-mile and 4-mile walks)
2. 3 Mile Weight Loss Walk
3. Exercise TV AHA Start! 3 Mile Walk
4. Punch Up Your Walk 4 Mile Walk
5. Walk Slim 4 Fast Miles
6. Walk Slim Fast Firming: 4 Really Big Miles
7. Walk Slim 5 Really Big Miles (the newest)
8. Advanced 5-Mile Walk
9. 5-Mile Fat Burning Walk
10. WATP Fat Burning Miles (Walk & Jog, Walk & Kick, Walk Strong & Power Mile)
11. WATP Ultimate Collection (1,2,3,4 miles, mostly the Express series)
ETA: On VHS I still - and will always - have WAP Abs 1-Mile Super Challenge.