Add egg whites before baking. They'll help hold its shape. Press firmly into pan and don't toss. Alternatively, use butter and sugar with baking soda as your "binder", essentially making a caramel crunch and then press into a pan as above. These techniques make crunchy bars

You can also use nut butters and honey/syrup for chewy bars, and they're best kept in the fridge. Once they start warming up, they can fall apart. Great for home use, but if you're sending them to school/work, I'd go the crunchy route.

I make a simple (loose) granola that everyone loves. What's the best way to transform this to make reasonably intact bars or chunks of granola?