Indigo League Addition
I just added episodes 38-52 to the new Part 2 of the Indigo League Screencap page. It got so long that it broke the length requirements on lj, so I was forced to split the series into two entries. Fair warning, the page might take a bit to load for dial-up users because there are four thumbnails as a preview for each episode.
These 15 episodes include such classic moments as Charmander's evolution into disobeying, the first of the many misadventures with Jigglypuff, James' past, the birth of Togepi, and the introduction of Butch and Cassidy.
The full directory of all Pokémon seasons is here.