I have found spaghetti squash to be a great substitute for spaghetti.
It has 15 calories for 2 ounces compared to about 200 calories for regular spaghetti. This means I can have a large portion for wayyyyy less calories!
I prepare it in the microwave. Poke some holes in a spaghetti squash and microwave for 2 minutes. Allow it to cool then slice it in half. (It makes it MUCH easier to slice if you microwave it first.) Clean out the seeds and pulp. Place 1/2 of the squash face down in about 1 inch of water and microwave for about 7 minutes. Allow it to cool. Use a fork to "flake" the squash into strands by running it down the length. It actually LOOKS like spaghetti!
My dh and I both love the taste! It has a slightly nutty flavor and crunch.
It is great with minced garlic, butter buds and parm cheese. It can be used with tomato sauce or in any way you'd use spaghetti.
Another use for it is for a "mock" coconut pie. I've made this before and it was pretty good. I used coconut extract for the flavor.