This recipe comes from Diana Rattray over at About.com (this recipe came up when I googled split pea soup). The original recipe is here, but I made a few changes based on what was available in my kitchen, and personal preferences. 
Slow Cooker Split Pea Soup, adapted from Diana Rattray's recipe
- 1 (16 oz.) pkg. dried green split peas, rinsed
- 2-3 cups diced ham (I like more ham, because it adds heft)
- 3 carrots, peeled and sliced
- 1/2 cup chopped onion
- 2 ribs of celery plus leaves, chopped
- 3 or 4 cloves of garlic, minced
- 1 bay leaf
- 1 tbsp. salt (or to taste)
- 1/2 tsp. fresh pepper
- 1 1/2 qts. hot water
- 1 15 oz. can sweet peas, with juice (orig. doesn't call for this, but I like the extra sweetness and heartiness it adds)
Preparation:
 Layer ingredients in slow cooker in the order given; pour in water.  Do not stir ingredients.
 Cover and cook on HIGH 4 to 5 hours or on low 8 to 10 hours until
 peas are very soft..  Remove bay
 leaf. Mash peas to thicken more, if desired. Serve garnished with croutons, or with a side of crusty bread.  
 
