@venam:
I found it very bad to start with every project that comes into
my mind. Even before I write the idea down, I think about the usefulness
of it, search if there is not already a similar project,
and then write it down.

@z3bra
>posix shell (yacc)
Do you want to write a standard compliant sh, or rather something
with useful extensions, or a completely new shell?

@novas:
I thought about doing something with voice recognition
as well, but after reading a bit into that topic I decided
that I am not crazy enough for this (yet).
>lambda calculus interpreter
I liked this one: https://github.com/mpu/lambda