I'm a huge fan of snacks.  It's funny how adults intuitively know that kids need snacks yet somehow think that adults don't.  There are lots of benefits to snacking, here are my top 5:

1. Snacks keep your blood sugar stable – Ever gotten "hangry?"  Not fun for you or those around you.
2. Snacks prevent overeating by preventing you from getting overly hungry.
3. Snacks help you think clearly because they fuel your brain with its energy supply of glucose.
4. Snacks fill in nutritional gaps in your eating by providing variety.
5. My personal favorite: Snacks taste good!