For me animation is the way to go on a comedown. I taped most of the BEAVIS & BUTTHEAD episodes when they originally aired & always pop one of the tapes in on the comedown.
SPACE GHOST COAST TO COAST or any of the shows on the OLD "Adult Swim" lineup (ie CARTOON PLANET and THE BRAK SHOW) do the trick as well (the sucky new Adult Swim lineup, ie AQUA TEEN & SEALAB is obvious & sophmoric junk).
The Miyazaki stuff like PRINCESS MONONOKE, CASTLE IN THE SKY, SPIRITED AWAY and MY NEIGHBOR TOTORO are also great on the comedown.
I also like to check out some of the old MST3K shows as well.