OmniFocus
From Brock University's Digital Humanities Compendium
OmniFocus is an organizer, project manager, task scheduler, and calendar all rolled into one convenient software. Projects can be given post-dated start dates, specific due dates, and contexts for completion. When dates approach, the program will notify you of the deadline through your choice of notification.
The Simulating History Lab at Brock University has created this tutorial to help digital humanists get started with OmniFocus.
More information and support can be found here.