In Vim using digraphs:
Ctrl-K f * → φ
Ctrl-K t * → τ
In general: Ctrl-K <latin letter> * → <greek equivalent> Ctrl-K f * → φ
Ctrl-K t * → τ
In general: Ctrl-K <latin letter> * → <greek equivalent>In emacs it's
C-| tex
then \phi → φ
etc, which can be quite a bit more typing but can be easier to remember if you already know the TeX instructions for everything.Now we just need to convince other editors to add something similar...
There are other ways of inputting digraphs: C-x 8 RET lets you enter the name of any unicode symbol.
I wrote about the many ways of inputting digraphs and unicode here:
http://www.masteringemacs.org/articles/2010/10/13/diacritics...