Can't believe I didn't stumble on this one until now. I love truck stops! But can't say I've travelled as much as many of you, nor kept track of all of 'em. The ones that come to mind off the top of my head, though:
Dysarts, already mentioned, Bangor ME. Top-notch food, low-key, not as noisy or smoky as many. Had a great Thanksgiving experience there a few years ago, my brother and I stopped by for some pie, it was snowy and cold, waitress gave us the story of her life and while it could have been all just for the sympathy, I felt it and tipped her $10 on a $10 order. Hey it was a holiday weekend.
Romines, Morris, Il. Home of the 2 pound burger. Have to admit right off I've never actually eaten there; place was always too jam-packed! Stopped there a couple of times on my way to Starved Rock state park from Chicago, and the wait was ridiculous. But I did get a glance at their baked goods which looked top-bakery quality, and I've heard great things.
P&H, Wells River, VT. In one of the Sterns' books, and deservedly so. Great maple cream pie, but basically everything's good. Nice atmosphere, seems to be the only place to eat for miles around.
The Pine Cone, Johnson Creek, WI. Also reviewed by Jan and Michael; I had to eat in the small smoking area if I wanted to eat soon, which I did; great breakfast included some of the better sausage I've had and perfect truck-stop coffee. Very cheap too.