User forums, mailing lists

• Cplex: http://forums.ilog.com/optimization/index.php
• Xpress: http://groups.google.com/group/xpressmp
• AMPL: http://groups.google.com/group/ampl
• Lp_solve: http://tech.groups.yahoo.com/group/lp_solve/
• glpk: http://lists.gnu.org/archive/html/help-glpk/
• Coin or: http://list.coin-or.org/mailman/listinfo
• Sci.op-research: http://groups.google.com/group/sci.op-research/

Update:

• AIMMS: http://groups.google.com/group/aimms
• KNITRO: http://groups.google.com/group/KNITRO
• Xpress new forum: http://discuss.fico.com/blaze/board?board.id=xpressdiscuss