RISM and IECM51.EXE compatible host system
Reduced Instruction Set Monitor
Intel
ftp.intel.com : /pub/mcs51/tools

ApBUILDER 2.0
Development system for the Intel MCS-51(R) family
Intel
ftp.intel.com : /pub/mcs51 and /pub/mcs96

PDSWxxx.ZIP
This is the 32-bit Windows IDE for PDS51, the Philips 80C51 and LPC family
emulation system. Can also be run as a simulator.
Supports all major compiler and assembler vendors.
Location: http://www.pds51.com

NoICE
PC-hosted debugger (NOT a simulator)
John Hartman <102203.1513@compuserve.com>

sim552vq.zip
8051/80C552 simulator (Freeware)
Brian Brown
cscnt.cit.ac.nz : /pub/intel/sim552v1.zip

Emily52
simulator
Shareware.
Dunfield Development Systems

BlowIT
Atmel 2051 programer
Freeware
Silicon Studio
http://sistudio.com/
 
 

ROM Monitor-based Debuggers

ChipTools (ChipView-51 looks like turbo debugger)
Dunfield Development Systems

Simulators

8052.com
Archimedes
Avocet Systems
ChipTools, Inc.
Crossware (simulator running under Windows)
Dunfield Development Systems
HiTech Equipment Corp.
Hitex
J & M Microtek, Inc.
Keil Software
Lear Com Company
Mandeno Granville Electronics, Ltd
Micro Computer Control Corporation
Microtek Research
Phytec
Phyton
Production Languages Corp.
PseudoCorp
SoftChip Ltd
Tasking Inc.