ITA has some clever challenges (including an archive of past puzzles):

http://www.itasoftware.com/careers/work-at-ita/hiring-puzzle...

But then that's the thing, a lot of places have these kind of programming challenge puzzles.

What's the closest to a Putnam for programming challenges?

I know Facebook is trying to position their Hacker Cup this way, but it had a rough start that makes you wonder if it's the best thing for Facebook to run on its own.

It seems like there's an opportunity for a prominent and widely-sponsored event run by a third party.

I presume the sponsors would love a window of exclusivity to see the best results from recruitable competitors.

Even without the obvious recruiting benefits, it would at least capture the imaginations of aspiring programmers worldwide.