"Time = Life, Therefore, waste your time and waste your life, or master your time and master your life." Alan Lakein.
I love Minuteur. It is a great way to do Now Habit timed project sprints as well as a way to keep track of billable time for freelancers. Freeware up through version 4, with a suggested donation of 8 euros (like, $12.25 or something).
A good cheat sheet on Neil Fiore's Now Habit is here, by the way.
I finally contributed since I use it so much and Philippe Galmel, the developer, sent me a link to the beta of version 5, which has some other cool, simple functions -- like being able to adjust the eggtimer ticking volume really LOUD when I need to be reminded that my Time Is My Life. Which, of course, is a reminder I need constantly.
I have put in a feature request for a cortex implant in version X for the rare occasions when I am away from my Mac.