Question

This is a great compiler for almost all important codes

Answer 1

http://codepad.org/
C
C++
D
Haskell
Lua
OCaml
PHP
Perl
Plain Text
Python
Ruby
Scheme
Tcl

Answer 2

gud 1

Answer 3

In fact, it's not ,the best is:

http://ideone.com/

*You can include standard input , more languages and you can save them.