There's some great stuff there: http://www.channel4.com/programmes/4od

I'd like this thread to act like a bookmark page, so add your recommendations below.

http://www.channel4.com/programmes/the-adam-and-joe-show/4od
http://www.channel4.com/programmes/the-ascent-of-money/4od
http://www.channel4.com/programmes/black-books/4od
http://www.channel4.com/programmes/the-book-group/4od
http://www.channel4.com/programmes/boy-a/4od
http://www.channel4.com/programmes/brass-eye/4od
http://www.channel4.com/programmes/britz/4od
http://www.channel4.com/programmes/buried/4od
http://www.channel4.com/programmes/the-camomile-lawn/4od
http://www.channel4.com/programmes/cold-lazarus/4od
http://www.channel4.com/programmes/dead-set/4od
http://www.channel4.com/programmes/the-deal/4od
http://www.channel4.com/programmes/father-ted/4od
http://www.channel4.com/programmes/free-agents/4od
http://www.channel4.com/programmes/gbh/4od
http://www.channel4.com/programmes/garth-marenghis-darkplace/4od
http://www.channel4.com/programmes/ghosts/4od
http://www.channel4.com/programmes/lipstick-on-your-collar/4od
http://www.channel4.com/programmes/nathan-barley/4od
http://www.channel4.com/programmes/north-square/4od
http://www.channel4.com/programmes/psychos/4od
http://www.channel4.com/programmes/queer-as-folk/4od
http://www.channel4.com/programmes/red-riding/4od
http://www.channel4.com/programmes/sex-traffic/4od
http://www.channel4.com/programmes/shackleton/4od
http://www.channel4.com/programmes/shameless/4od
http://www.channel4.com/programmes/spaced/4od
http://www.channel4.com/programmes/teachers/4od
http://www.channel4.com/programmes/traffik/4od
http://www.channel4.com/programmes/ultraviolet/4od
http://www.channel4.com/programmes/vic-reeves-big-night-out/4od
http://www.channel4.com/programmes/wedding-belles/4od

If you only watch one programme that you didn't catch when it was broadcast, then I'd suggest Buried. Top stuff.