You can download an evaluation version of the IAR Embedded Workbench IDE from IAR's web site http://iar.com/website1/1.0.1.0/675/1/
There are two different evaluation versions of IAR Embedded Workbench
The 30-day evaluation edition contains fully functional 8051 compiler, assembler, linker, and debugger. Code size is unlimited, but it has a 30-day time limit.
The kickstart edition contains a fully functional 8051 compiler, assembler, linker, and debugger. The code size is limited to 4 Kbyte, but there is no time limit.