This is the blog of Ronald Bartels that wanders on and off the subject of problem management (that is how it started), but it is best described by Ray who says this is Daddy's thoughts! Like the best music is from the Eighties and a wee dram helps in solving most inconveniences.
OpenNMS is a carrier-grade, highly integrated, open source platform designed for building network monitoring solutions.
There are two distributions of OpenNMS: Meridian and Horizon. Using Meridian is advisable for enterprises and businesses looking for stability and long term support. Horizon is the place where innovation happens quickly and is ideal for monitoring new technologies and IT ecosystems. Both distributions are completely open source.
Download the tool here or checkout the more comprehensive list of tools here.