You can make pesto with basil, arugula, and many other greens. Super easy:
4 loosely packed cups of greens
Juice from 1/2 lemon
1/4 cup olive oil (or to taste)
1/2 teaspoon salt (or to taste)
1 clove garlic (or to taste)
Zap in food processor until smooth. Makes about 1/2 cup. Freezes well.