I got this recipe from allrecipes.com and didn't make any modifications except I used soft taco shells. It was delicious, cheap, and easy.
1 cup finely chopped onion
1 garlic clove, minced
1 teaspoon canola oil
1 cup dried lentils, rinsed
1 tablespoon chili powder - instead of the chili powder, cumin, and oregano you can just use taco seasoning
2 teaspoons ground cumin
1 teaspoon dried oregano
2 1/2 cups chicken broth
1 cup salsa
12 taco shells
taco toppings: lettuce, tomatoes, sour cheese, cheddar cheese
1. In a large nonstick skillet, saute the onion and garlic in oil until tender. Add the lentils, chili powder, cumin and oregano; cook and stir for 1 minute. Add broth; bring to a boil. Reduce heat; cover and simmer for 25-30 minutes or until the lentils are tender. Uncover; cook for 6-8 minutes or until mixture is thickened.
2. Stir in salsa. Spoon about 1/4 cup lentil mixture into each taco shell. Top with lettuce, tomato, cheese and sour cream.