mikroC - mikroC is a full-featured ANSI C compiler for 5 different microcontroller architectures. It is the best solution for developing code for your favorite microcontroller
CPIK - the C compiler for PIC18 devices
Dcoder - Dcoder is an online compiler, a cloud based IDE for mobile and desktops, where one can code and learn algorithms. Now code, compile, run anytime anywhere.
CCS PCW Compiler - CCS, Inc.
Tiny C Compiler - The Tiny C Compiler is an x86, x86-64 and ARM processor C compiler created by Fabrice Bellard.
Portable C Compiler - pcc is a C99 compiler which aims to be small, simple, fast and understandable.