If you or your loved ones like relish (or salsa verde for that matter), I have the perfect solution for your green tomatoes. It came from Farmgirl Fare with some very small adaptations from me.
Many of her commenters said it reminded them or green salsa. This is true, although with the amount of vinegar listed, there's something distinctly relish-y about this. If you really want a salsa verde, I'd reduce the vinegar to 1/4 C or even just 2 Tbsp and maybe use lemon or lime juice instead of vinegar.
If you plan to can it, you'll want to use 1 C vinegar in order to make it nice and acidic and safe.
We used it in our taco pie the other day with a little red salsa and it was GREAT.
Savory Green Tomato Relish
adapted from Farmgirl Fare
makes 3 pints (we halved it since we are not huge relish eaters and I didn't want to can)
Prep and cook time: 30 minutes
(tomatoes: come on, they're free, onion: .15, red peppers: .75, apple: .50, jalapeno peppers: .50; other stuff: .10)
2 lb (about 12-16 romas) green tomatoes, cored and chopped (make sure they are hard green tomatoes)
1 lb (1 large) white or yellow onion, chopped
3/4 lb sweet red peppers (2-3), cored and chopped
1/2 lb tart cooking apples (1 large) such as Granny Smith, cored and chopped
6 garlic cloves, finely chopped
1/2 C apple cider vinegar (use 1 C if you plan to can; 2-4 Tbsp if you're going for a salsa)
1/2 Tbsp salt
2 jalapeno peppers, cored and seeded (Farmgirl recommends 4, but we're weak in the heat department)
2 Tbsp chopped cilantro
1 tsp ground cumin (optional)
Combine tomatoes, onions, peppers, apples, garlic, vinegar, and salt in a large nonreactive pot (such as stainless steel or ceramic) and bring to a boil. Reduce heat and simmer, uncovered, stirring occasionally, until vegetables begin to break down and it all seems thicker.
Stir in jalapenos, cilantro, and cumin and simmer for 5 more minutes. Put mixture in blender and blend until chunky (or use an immersion blender). Don't get it smooth.
This will keep for several weeks in the refrigerator.
If you want to can it (I didn't so these are Farmgirl's instructions): Ladle hot relish into hot jars, leaving 1/4 inch head space. Process in boiling water canner for 15 minutes. Store in cool, dark place for up to a year.