I am a fan of Aldi, but I usually go to the one in St. Leon-Rot, since it's closer to home.
Aldi has pretty much all your basic grocery needs covered, plus the "random crap I don't actually need to buy but can't resist" section right in the middle of the store. It has great home deco stuff, various sport clothing articles, and sometimes even fashion items, all for a very decent price.
Go here for great fruit/vegetable and dairy products, as well as your basic staples. If you are looking for more exotic things, like say guacamole mix or tortillas, I usually go to Rewe for that. But for the basics, it's really good.
Oh, and their bread is excellent. read more