Teacher training is a very important and really necessary part of their professional career. Two long-term activities aimed at Czech physics teachers are presented in the paper: "The Heureka Project" and "Elixir for Schools".
These activities are based on voluntariness principle; teachers attend them because they want, not because they are forced to be there by somebody (e.g. their headmaster). These projects can be taken as examples how informal system of teacher education can be created and developed as a useful counterpart to a formal in-service teacher training system.