MachDB is machine database to catalog of the changing state of your hosts. It consists of a database, an aggregator, an XML spec, and some example information gathering scripts. Along with a Web UI, these form the basis of a system that will allow you to catalog the current and historical state of the hosts in your infrastructure. It has been designed with scale in mind, and the goal is to support 10k hosts. It is being actively developed and is used in production at a few organizations.
cronbot is a wrapper script for cron jobs. Rather than running your job/script directly, you run it through cronbot, and it will allow a little more control to help keep things from getting out of hand. The default behavior is to only allow one instance of your job to run. This can be changed with the --duplicate option. You can also pass in a maximum time of execution for a job or add a random amount time to delay the start of your job. By default, jobs are run with a default "nice" value, which is usually 10.