For spaghetti (if you mean sauce), we like
Emeril's Turkey Bolognese (although it makes a HUGE amount - at least it freezes beautifully).
Can't help for tacos. We usually eat carnitas or fajitas as soft tacos.
For sloppy joes, we tried
Ellie Krieger's recipe once and liked it.
For chili, keep in mind we are in Texas and Texas chili has no beans in it. Beans on the side = perfectly fine. Beans in your chili = gosh darned cotton pickin' Yankee! For from scratch, you can't beat
Tom Perini's Ranch Chili. If you want an awesome mix,
Cin Chili is fantastic (and much better than the faux recipe on Food Network's site). I can find this in our local grocers here in Texas (and I do modify it by browning a diced onion and a few cloves of minced garlic with the beef). Tastes like you cooked the chili for hours.
Oh, and always use good quality, fresh spices. I get my chile powders (and chili powders) from Penzey's.
Michelle