It seems that the liftIO function from MonadIO can be generalized to access whatever the base of a transformer stack happens to be. So there is no need for a liftSTM, liftST, etc.
This is by Iavor S. Diatchki and can be found at http://www.cse.ogi.edu/~diatchki/monadLib/
It is a new version of the mtl package with transformers: ReaderT WriterT StateT ExceptT SearchT ContT
It also defines BaseM which is like MonadBase above.