vanko:I thought that F# is official too. See this link
IronPython, IronRuby, Vbx are also official. They are developed by Microsoft to support the DLR.
F# is not a new language, it was under Microsoft research for many years, and now been implemented to .net 3.5.
Pleasenote, VB.Net, C#, F#, IronRuby, IronPython, Vbx, LoLcode are all official to .Net. The only reason is few of them are still under alpha stage.
Ruby and Python are most popular dynamic languages and hence it was considered by MS to develop it to support DLR. Very soon, you will find the languages discussed everywhere on the net, once they are released as Beta or Final Version.
Thanks