I like One Tree Hill, its probably my favorite pure coming of age show (i.e. non-fantasy). Generally like Seasons 1-4 more than the later stuff, tbh most shows like this are better during the high school years, and unlike Buffy there is less reason for everyone to hang with each other after that point which makes the charecters draw apart a little from Season 5 onwards.
Did occur to me some paralels can be found between OTH and Buffy charecters. Lucas reminds me a little of Angel in some ways, Nathan of Spike, Hayley has a slightly Willow vibe especially early on, Brooke is a bit like Cordelia (although a little nicer), Rachel would be Faith, Karen is Joyce, Keith would be Giles, and I guess Mouth is Jonathan if he had friends.
Can't remember what its called, but there is a pretty good OTH/Buffy crossover on Archive of Our Own. Brooke, Peyton and Hayley are magically summoned to Sunnydale to help deal with a new big bad. The ending is pretty sad with a character death, though I suppose that's par for the course in the Whedonverse.