For instance the golang.org website is running on Go: http://golang.org/doc/go_faq.html#Is_Google_using_go_interna...

Google open sourced vitess for scaling out and coordinating (sharding + replication, schema rollouts) mysql databases, it seems they use it internally: http://code.google.com/p/vitess/

P.S. Other organizations using Go: http://go-lang.cat-v.org/organizations-using-go