Assembler Gems
Intel x86 and Motorola assembler snippets. Good collection of assembler algorithms in an easy to read format.
http://www.df.lth.se/~john_e/gems.html

Systems/Asm
Home page for Dignus,LLC - producers of language tools for the IBM mainframe.
http://www.dignus.com/

Mainframe Express Assembler Option
Micro Focus' unified environment for mainframe development significantly reduces risks and costs, and offers improved business agility through extension to J2EE, .NET and Web services
http://www.microfocus.com/products/mfeee/

terse
Algebraic assembly language employing prefix, infix, and postfix notation. Assembler simplified. Biggest advance in low-level programming since Macro Assembler. All the control of assembler, with the ease-of-use and look-and-feel of high-level languages. Low cost.
http://www.terse.com/

8051 Macro Assembler ASEM-51
8051 Macro Assembler ASEM-51
http://plit.de/asem-51/

NIH Computer Center - Using Assembler Language
Inhouse doc for NIH, but also contains general assembler programming tips.
http://datacenter.cit.nih.gov/assem/

Atari 6502 - Cross Assembler
The Social Media blog is your single destination for updates on the AIM Buddy blog, the AIM Pages blog, the AOL Community Info blog, the Expressions Factory, the Marvelous Mob and the Social Media Mess blog.
http://members.aol.com/MacFalkner/atari/assi/index_e.htm

ARM Assembler
A resource that is, no doubt, useful for those whose French is better than their English who want to program in ARM assembler. [Vincent Lefèvre]
http://www.vinc17.org/acorn/riscpc_eng.html

Assembler for the mainframe
HLASM - High Level Assembler Language
http://www.sysprog.net/hlasm.html

The Assembler Connection
SimoTime is a technologies and services company providing tools and skills for the integration or conversion of mainframe legacy and web systems for the Internet or Intranet environments. We can quickly convert BMS and MFS screens to HT ML fo rms that include JavaScript to handle specialized functions.
http://www.simotime.com/sim4lib1.htm#ASMConnect