Someone hold me back from the temptation to just copy and paste the Hufflepuff welcome message here.
Instead, I'll just copy this from the Harry Potter Wiki,
Helga Hufflepuff article:
Now it may not necessarily say that we have the recipes, but keep in mind that it was Helga who kept the place fed, and that our Common Room is right next to the kitchen.
Now, as far as reference in the books goes, you're right, there's not a whole lot. But you bring up Cedric Diggory, don't you? Why do you think a Hufflepuff was chosen over all of the others? There was significance in that. A Hufflepuff embodies what a competitor for the Triwizard should be, someone who is worthy, not someone who will cheat and scheme to win, not someone who will barrel in without a brain cell to spare, not someone who will just sit there thinking it over and therefore delay their loss; no. A Hufflepuff was the most worthy choice, because they would play fair, play smart, and play strong. Cedric Diggory was the one who said "Hey, I'm sorry about all the Harry Potter hate," the one who told Harry how to open his egg, was the one who wouldn't leave Harry's side in that graveyard.
So when you think about it, Cedric Diggory was a HUGE character. He marked a new era, and Harry carried his death with him through the rest of the series. And can we please remember that Nymphadora Tonks was a Hufflepuff too? Susan Bones, who Neville goes on to marry, was a Hufflepuff.
Also, if we're basing all of these opinions purely off of the books and movies, the only Ravenclaw that was really a serious help was Luna Lovegood. Cho was.... annoying, to say the least, and no other Ravenclaws are coming to my mind... well, unless we count Marietta Edgecombe, who sold out Dumbledore's Army. Wouldn't catch a Hufflepuff doing that, would you?