Language selection would be good too - possibly by excluding uninteresting ones rather than actively including them though. This would keep the results slightly surprising; the point is just to let you ignore languages that might otherwise be overrepresented.

See, e.g., http://githut.info/ - if you're not interested in one or more of Javascript, Java, Python, PHP, C, C++ or Ruby, you could easily see a lot of uninteresting projects.

This does sound a lot more useful. The majority of GitHub users don't have any real projects. Maybe only showing GitHub users that have more than n followers would be better.