It has been a really long time since I looked at quant forums. i couldn't remember their names and somehow didn't have them in this doc. So, for future reference, here they are:

• http://www.nuclearphynance.com/
• http://wilmott.com (blogs, too)
• https://www.quantnet.com/
• https://www.bigmiketrading.com/
• http://www.trade2win.com/boards/
• http://www.elitetrader.com/et/index.php

here's a new one i just found

• http://www.rajeevranjansingh.com/order-matching-execution-side

and here is a rarely updated blog that has links to great references

• https://mathtrading.wordpress.com/