Two I can think of off the top of my head: "The Bitter End" sounds like "Battery" by Metallica and "The Jester" sounds like "House Of Wolves" by My Chemical Romance. There are a few more, but those are the most notable. Don't get me wrong, I do like Sum 41, but I've noticed that they're not the most original.
Oh, and the first thing yelled in the Sum 41 song is almost the same rhythm used in Chop Suey. "Take everything left from me" is the same as "when angels deserve to die".
I still like We're All to Blame, though. It's a good song in itself, even if every time I hear it, I think of Chop Suey.
It's weird with Sum 41.
They had that...third album was it? Which was all pretty much blatantly Offspring-sounding. Then the next one was totally "spot the Metallica references".
And it didn't ever bother me. I don't even like the band, but I guess them copying other bands blatantly made them better than their "own sounding" stuff was anyway. That Offspring-esque disc of theirs was actually kind of fun.
On the flip side though, it pissed me off to no end on RAFRAG, with all the Green Day sounding stuff in the second half. Hypocrite is me.