It is as good as (better, actually) than store-bought, and -- like the pumpkin spice blend -- utilizes spices you probably already have on hand.
My version is adjusted and tweaked from different recipes, but is largely based on (surprise!) Alton Brown's.
2 Tbsp chili powder
2 Tbsp cornstarch (you can omit this, but the sauce may be a little thin/watery)
1 Tbsp ground cumin
1 Tbsp Kosher salt (or 1-2 tsp table salt)
1 1/2 tsp smoked paprika
1 tsp ground coriander
1/2 tsp cayenne (omit if you prefer it with little to no heat)
1/2 tsp black pepper
1/4 - 1/2 tsp garlic powder
1/4 - 1/2 tsp onion powder
Mix together all ingredients and store in airtight container.
Use 2-3 Tbsp per pound of meat/tofu/veg/whatever.
Add 1/4 cup of water while cooking, and let simmer for a few minutes until reduced/thickened.
And there you go - no more trips to the store for taco seasoning packets!
Added bonus: YOU control the amount of sodium content. Many of the store-bought packages are LOADED with sodium (some as high as 800+ mg!).