Ever since I found out that the banana chips you buy in the 'health-food' stores are deep-fried (how did I think they made them so crunchy?), and most have added sugar as well, I've been making my own.
Spent £2 to buy 30 bananas at the market this morning, and drying will let them keep in the fridge for a couple of weeks (store them in an airtight container).
To make, peel them, then stick your finger into the end and they'll naturally split into three long pieces. Put these on a non-stick making sheet, and bake them slowly (100 C, or maybe 175 F?) for a couple of hours, turning half-way through. Make sure they're really dry and chewy before you take them out.
So sweet and chewy. Completely different flavour from regular bananas.