Guido wrote the NDB framework for AppEngine, which, as an AppEngine user, I'd say has one of the most clever ways to do async requests that I've seen in any major language. I'm used to the C++ frameworks for async that are used in the main search stack, and switching to AppEngine and having things pretty much "just work" has been great.

He also did Mondrian, which kicked off the trend toward web-based code-review and was a huge step forward from just critiquing patches over e-mail.

Usually famous programmers get famous because they've done a lot of programming; that experience translates into some pretty cool programming chops.