Hey John, very good of you to point that out but believe it or not I left it out on purpose (as well as project management apps). This post was designed for general businesses and for the sake of brevity I felt that those tools are better suited for another post that I will be publishing which is geared more towards in the online and creative industries.
As a sneak peek, the time tracker I use and love is Toggl. They offer a free plan which is great for solo freelancers and does a spectacular job, but I think once you get a team then it is probably worth going for the pro plan. You should give it a go and let me know what you think. By the way, what sort of freelancing do you do?