We eat a lot of noodles with red sauce at our house (it's the only way I can get my kids to eat zucchini, bell pepper and carrots), so I've had a lot of time to figure out what add-ins we like.
I take 1 jar of spaghetti sauce (I like Ragu Robusto line) and 1 14 ounce can of tomatoes as my base.
Then, I saute in a little olive oil:
1/2 pound chicken sausage (note: Arizonans, I love Sprouts' "Mild Arizona Chicken Sausage")
1/2 pound ground beef
1 bell pepper (yellow is my favorite)
2 stalks celery
handful of baby carrots
1 zucchini, grated (I'm not a fan, but in the sauce, it just melts away)
1 med onion
3-4 garlic cloves, minced
At the end, if I'm feeling really fancy:
1 T fresh oregano
1/4 c of basil
Then, I add, oh, a lot of goat cheese (1-2 ounces) to Nate's and my portions.
Do you have pasta add-ins?