Another good idea is to check out your local library non-fiction section. Try under 306 (world cultures), or between 700 and 709 (arts and crafting, knitting, crochet etc). It's amazing the resources you can find just by browsing around the shelves!
This book isn't arranged like many others - but it comes up with several different cultural ideas based around a theme. For example it'll talk about farming in England, then suggest you take a trip to a cheese shop and try a variety of different cheeses from around the world. Or you'll learn about New Years' day customs from five different countries.
This one divides the world into regions, then suggests 2-5 dishes from that region, along with a little bit of history of that particular foodstuff. The instructions are simple enough for Sparks too!
I love this book - it divides the games into icebreakers, water games, running games, etc. There are also tons of suggested variations for small and large groups, as well as variations for various ability levels.
This really isn't a great field manual, but it's wonderful for brushing up on your own outdoor skills, as well as giving some great ideas for camping with Brownies and getting out there!
This book is fabulous because it not only gives great songs from around the world, BUT it also comes with a CD, so that you and the girls can hear the proper accent/tune for the songs as well.
If you're doing Guides, and not Brownies or Sparks, this also comes in a Grade 4-6 book as well. I like these because they're a bit more involved than regular crafts, but would be great for a sleepover or longer event.
This divides into countries, then by project. Some of the ideas are a little simple - but are sometimes just what you need for Sparks. You could even have the girls choose something for a Bridging meeting with Sparks.
All of these books are available on Amazon - or check out your local library!