I first ran into Justin Sweet's work on some of the recent Robert E. Howard collections. A fan of Frazetta, Sweet's style is a bit more mellow, but still has a lot of personality, not to mention beautiful details. His website has some good stuff too, here's a few samples:
The image above is one of my favorites, a scene from the Kull adventure "The Shadow Kingdom". You can almost hear the snake-men hiss. The detail of the tapestry and Kull's skirts are great too.
Apparently another Kull scene. This one resembles any number of Frazetta action scenes, with the hero above a pile of aggressors. Justin seems to be the go-to guy for Frazetta style art judging by his book covers and concept art.
The treacherous path along lonely seaside cliffs. You can nearly taste the brine in the foggy air. Feels just right as the party makes their way from the last outpost of civilization to some mysterious, legend-haunted coastal castle.