I've never seen a recipe for canteloupe or rockmelon(that's what we call them) muffins, but I can't see why you couldn't puree them & use them like you would any fruit puree. If you do it & it's successful please let us know as I have a fondness for muffins! Here's one we use for breakfast when they are real cheap here. Just replace the Splenda with sugar if you don't use sugar substitutes.

CANTALOUPE & YOGHURT SHAKES
Serves 4
1.15kg rockmelon cubes, about 2 melons
1/4 cup lime juice
2cups vanilla low-fat yoghurt
2tbsps Splenda

Puree until smooth. Serve in tall chilled glasses.