Disassemblers

High Level Assembler and Toolkit (HLASM) - System/390 assembler toolkit for MVS and VM and VSE (HLASM) including disassembler, by IBM.
http://www.ibm.com/software/awdtools/hlasm/

Application-specific Decompilers - Catalog of decompilers.
http://www.itee.uq.edu.au/~csmweb/decompilation/application.html

the bastard disassembler - *NIX disassembler. Written in C on Linux for x86 ELF files; intended to support multiple CPUs, OSes, and file formats. Scriptable.
http://bastard.sourceforge.net/

Misosys Disassembler - Tim Mann's TRS-80 Page includes Misosys Disassembler, aka PRO-DUCE.
http://www.tim-mann.org/trs80.html

FARGDIS - Fargo Disassembler for TI-92 DOS versioin, by John Grafton.
http://www.ticalc.org/archives/files/fileinfo/4/452.html

SST Global-Decompilers - Decompilers for IBM midrange systems.
http://www.sstglobal.com/

The dcc Decompiler - It decompiles small .exe files from the (i286, DOS) platform to C programs.
http://www.itee.uq.edu.au/~cristina/dcc.html

Transputer disassembler. - By Andy Rabagliati.
http://www.wizzy.com/wizzy/dasm.html

TRACE32 - Microprocessor Development Tools include multi processor emulators and disassemblers.
http://www.lauterbach.com/

AVATAR - A disassembler/patcher/code-explorer for PA-RISC based HP-UX systems, by Allegro Consultants, Inc.
http://www.allegro.com/products/hp9000/avatar.hpux.info.html

MacNosy - Is a Mac application that disassembles the Macintosh ROM or any 68K or PowerPC codes, by Jasik Designs.
http://www.jasik.com/nosy.html

DSP5600x - A 5600x disassembler by Miloslaw Smyk.
http://wfmh.org.pl/projects/delfina/

MELPS7700 Disassembler - By H.Kashima.
http://kaele.com/~kashima/software/melps7700e.html

Reverse Engineering Compiler - Program that tries to make source coden (C) from binary, multiplatform. There are MIPS disassembler too, by Giampiero Caprino.
http://www.backerstreet.com/rec/rec.htm

This96 - 80196 disassembler by zartoven.
http://www.winsite.com/bin/Info?500000032198

IDA Pro - The multi-processor, multi-OS, interactive disassembler, by DataRescue.
http://www.datarescue.com/

Re39 - Interactive Disassembler for Rockwell C29/C39 (C40) code by Lewin A.R.W. Edwards.
http://www.zws.com/products/re39/index.html

Universal Cross Disassembler - XDASM - DOS based cross-disassembler supports numerous processor types, by Data Sync Engineering.
http://www.datasynceng.com/xdasmdoc.htm

Open Reverse Code Engineering - An open community site offering a number of services including blogs, forums, download and reference libraries.
http://www.openrce.org