One of the better reference sites out there is called Texas Leaguers – The Mechanics of Baseball, and is run by Trip Somers. If you haven’t been there before, I definitely recommend checking it out. Trip offers mechanical analysis of a lot of pitcher, mainly Rangers, but also has and detailed glossary of a lot of the mechanical terms you sometimes hear, but have no clue what they mean.
One of the coolest features on Texas Leaguers is the online Pitch f/x web tool, which I didn’t know existed until Mike Fast brought it up a couple of weeks ago. Unlike Dan Brooks’ tool, which only gives you game by game data, Trip’s allows you to select the exact time frame that you want the data from for both batters and pitchers, and allows you to view multiple splits. For example, here are some charts about Tim Lincecum’s changeup this year. You can see that he consistently locates down and to the first base side of the strike zone. No wonder why it’s been one of the best pitches in baseball. You can also view charts for individual gamelogs, found on the sidebar, and some descriptive stats on the pitch.