Bill Melendez Productions is the excellent homepage of animator José Cuauhtemoc "Bill" Melendez. It gives a nice overview, in pictures and words, of the life and work of one of the great living animators.
As the bio on the site mentions, Melendez started animating for Disney, and then moved to Warner Brothers, where he stayed for the better part of a decade (minus a stint in the army during WWII). He animated for director Bob Clampett, then for Clampett's successor, Art Davis. When Davis's unit was shut down, Melendez moved to Bob McKimson's unit, but he wasn't happy animating for McKimson; like a number of animators, he felt that McKimson had overly rigid ideas about what constituted good animated "acting," and wouldn't allow animators enough freedom. (McKimson and Davis, promoted to director at WB within a few months of each other, had sort of complimentary strengths and weaknesses: Davis was good with animators and kept a consistently strong animation team, but displayed a lack of confidence when it came to stories and had trouble keeping a story man; McKimson was arguably better with stories and certainly better at creating recurring characters, but had trouble holding on to animators.)
Melendez left Warner Brothers about 1950, and moved to UPA, where he animated on some of that studio's early successes, including "Gerald McBoing-Boing." His subsequent work, as a producer-director of commercials and television specials, often showed the influence of the UPA studio style in its use of stylized backgrounds, character designs, and movement, and the conscious adoption of drawing styles that wouldn't normally be considered animation-friendly.
His ability to adapt other cartoonists' drawing styles to animation made him the perfect choice to direct "A Charlie Brown Christmas," where he solved the problems of animating characters who were hard to animate: in the strip, Charlie Brown is usually seen only from two angles -- front and side -- so Melendez and his team had to work out all the details of what Charlie Brown and co. would look like when they turned their heads, how they should move, and so on. They did it so well that people often mix up the way the characters are drawn in the TV shows with the way they're drawn in the strip; the adaptation is seamless enough that it seems a natural extension of Schulz's drawing style. Melendez went on to direct most of the "Peanuts" specials and movies, and produce the ones he didn't direct; he also did the same for the "Garfield" specials.
His style as an animator was of the loose, fluid variety, showing his Disney training (like Emery Hawkins, with whom he worked in the Davis and McKimson units). He had an interesting way of making the characters hold up both of their arms while the rest of their bodies move freely and fluidly. It's not wild, broad gesturing; it's more something to focus on amidst the more-or-less free movement:
("Falling Hare," Clampett)
("Baby Bottleneck," Clampett)
("Bowery Bugs," Davis)
("An Egg Scramble," McKimson)
Melendez turns up in several featurettes and audio commentaries on the Looney Tunes DVDs, which are also where I got the screencaps. Unfortunately the DVDs of the Charlie Brown specials don't have any special features, so there's no chance to hear from Melendez on the subject of his biggest successes.