What languages used to write computer languages?
daeken: A good deal of higher-level languages are completely bootstrapping.  C#, Nemerle, a good number of Scheme implementations, etc all compile themselves.  You of course have to write your initial implementation in something else, but once that's done many compliers bootstrap themselves completely.  In fact, when I design a language I write the smallest implementation possible before bootstrapping up (as I'm doing with Dynemerle, a reboot of the Nemerle project).