We just had one recently (though I didn't go this year because of gas prices). My LQS usually runs it for our state. We have 18-20 stores that participate. We do buy the passport, but we get a tote bag (like the ones you buy in the supermarket for 99 cents) and each place puts a stamp in your book. The last one I went to, each place had us pick out two strips of 2 1/2" wide fabric. If we made it to all the shops, our home quilt shop would give us the pattern for free and we had enough strips to make the pattern (just needed to buy background fabric).
Each store will have refreshments and a snack for us and has a special just for the shop hoppers. It's a wonderful way to go to shops you have not been to and it's also really nice to go with a fellow quilter.