The inestimable Charles Pierce says most of what I'd say about Levon Helm - what I'd say if I was as Irish eloquent as Pierce. I'm not, so I'll refer you to him. (And I like Pierce's idea of outpouring the love now, while there's a chance some of the vibes might make it Levon's way.)
All I'll add is a few of my favorite little touches of Levon. Like, it seems, most who heard them, the Band touched me deeply - defined a particular kind of faith in the unseen, made you believe in an America that you just couldn't, can't, find much in evidence around you. But they also just taught me a lot on a musical level - they're like the finest of wines or the craftiest of craft beers, every sip a complex combination of grace notes and oblique attacks. These are pretty obvious choices, but worth savoring anyway.
"When I Paint My Masterpiece." As a Levon number this is a bit unexpected, because of course he sat out most of the Band's extended dalliance with Dylan. But he does this song justice. And if you need reminding of just what a sensitive, character-ful singer the man was, notice how he pronounced "everywhere" in "ancient footprints are everywhere." That aspirated "wh" - it totally sells the lyric. The speaker in this song knows he's not much in the face of all this glory, but he's still got a little bit of dignity. He's not defensive, either. He's just going to do the Old World the politeness of speaking correctly. That or it's just the way Levon sings, but damn: it fits.
"Daniel and the Sacred Harp." Levon only sings half of this one, of course, but he does it with his usual elan. Listen to how he handles the climactic verse: "Then to his father Daniel did run / and he said Oh Father what have I done? / His father said, Son, you've given in / you know you've won your harp but you're lost in sin." Listen to the touch of delirium he brings into the second line there - "Oh Father" - not enough to overpower the melody, but enough to scare the bejeezus out of you, for sure. And yet not enough so's he can't turn right around and give the father's words all the matter-of-fact moral weight they need, too.
"Don't Do It." Nobody but nobody could rock soul music like the early Band. And everything about this track is Levon. He plays and sings the fuck out of it. Listen to that little swaggery stutter he puts on the beat (he was, as somebody - Greil Marcus? - once said, the only drummer who could make you cry with his drumming). And the way he shouts "PLEASE" - this is the kind of scream that tenses your neck muscles and your collarbone.
Okay, here's a less obvious choice. Levon belting out "Further On Up The Road" back when he was a Hawk. The thing about the Band, see, is that they were basically the only American rock act of the late '60s and '70s who owed exactly nothing to the British Invasion. They didn't need the Beatles to entice them, or Dylan to permit them, to switch from folk to rock. Levon learned from one of the actual original rockabillies, the Hawk, and the rest of the Band, straggling in one by one until it was the Band, did too. They were always playing rock and roll. Blues. R&B. Levon was not turned on to the blues by the Rolling Stones or the Yardbirds, but by listening to Sonny Boy Williamson his own self. Dig how at the 2:10 mark or so he's singing it: "'uthah on up the road". And then at 2:30 that dirty growl: "aaaanggg!" He completely owns this song.