I've created a website to house all my M*A*S*H screencaps (click the banner). Eventually my plan is to have all episodes of all seasons capped in DVD quality on the site. Currently all of season 3 is capped and online, as well as a couple episodes from season 1 and one from season 4, for a current total of 27 episodes/13,084 screencaps.
The site is a resource, so please feel free to download the caps and use them as you will. Just don't claim as your own or redistribute, of course. I don't require credit, though a link back to the site (http://www.geocities.com/mash_caps/
from White Gold