Jenkins Priority Sorter Plugin
This plugin adds the ability to assign different priorities to Jobs, the lower priority the job has the sooner the Job will run.
This can be very helpful when one wants to add low priority jobs but wants to have higher-priority jobs run first when hardware is limited or when there are different groups of Jobs that should share resources (equally).
The plugin both contains ways to select a Sorter Strategy and one or more Priority Strategies.
The Sorter Strategies will allow you to select how you want the queue to be sorted. This allows you not only to run higher priority Jobs before lower priority Jobs, but also to use algorithms such as Fair Weighed Queueing.
The Priority Strategies will allow you to have different priorities based on how the Job is started. This enables you to give Jobs started directly by a user higher priority than Jobs started by cron or by a commit.
See Jenkins Wiki @ Priority Sorter Plugin for more information.