Toggl desktop app or http://www.hrmacapp.com

http://www.timelyapp.com/ - best time tracking software I've ever used. Creates really easy invoices for your clients and the web UX is excellent.

Toggl is nice and has both web and desktop support. Loads of features in the paid version, but the free version offers basic tracking.

https://www.toggl.com/

I have been happily using Paymo for a couple of years or so. It has both OS X and Win native clients – data is stored online but you can use the time-tracker offline and sync it later.

Besides the time-tracker you can generate reports per task/project/client if needed prior to invoicing.

There's a free 'freelancer' account limited to 3 projects.

Hi, I would like to suggest a free time tracking tool https://tmetric.com/ for work session monitoring, tags for working time categorizing, reporting tools, browser extension UI, integration with popular project management systems like Asana, Basecamp, Jira, Redmine, Trello etc.

Maybe you want to try timelog.klwws.de. We're currently working on projects and accounts.

+1 for Toggl

I have used this before: http://www.timeedition.com/en/index.html

Otherwise toggle desktop

I like the look of hr like other people have suggested. I'll have to try that out. Personally I use Harvest because the time tracking is good enough but the invoicing makes my life easy for freelancing.

Not free, but may be worth $8.99

https://itunes.apple.com/us/app/tyme/id670592452?mt=12

A friend of mine loves it.

Tictoc is pretty nice. http://www.overcommitted.com/tictoc/

I use Toggl, but TimelyApp does look good too.

I think you should track the quality and not the time of your work. :)

I've been using a tiny app called Time Tracker for OS X for the last five years. It hardly ever gets updated and doesn't look sexy, but it gets the job done (and it does work on Yosemite).

this is a web-based app, but it is cool: http://tomato.es

I use a tag team of Harvest and Timecop.

Hours is excellent.

The app also makes great use of iOS 8 widgets by letting you start and stop timers right from the widget.

EDIT: Apologies! This doesn't fulfill your request for an OSX app, but Hours is still recommended.

Since you’re mentioning multiple projects I wanted to mention my app Caato Time Tracker+ as well: http://www.caato.de/timetracker+

It’s very simple and streamlined for painless, manual time tracking. Our free plan lets you track multiple projects, add notes, export your data to CSV and send it via email with only a few clicks.

Our pro plan ($4.99/month) offers folders, Excel export and realtime syncing to our iPhone app and other Macs.

Hi! You may want to check out my app Timing for Mac. It's not free, but if you are making money as a freelancer it should be well worth it.

It's different from other time trackers in that it automatically tracks all the time you spend in different apps. You can then later assign that time to your projects and even extend the data. Makes your time tracking way more accurate than any manual time tracker! And of course you can export the data for invoicing :-)

+1 for Toggl! Thank God I found this thread. 30 seconds of (free) use and it's perfect for my rather-simple needs. SUPER easy - hence it only took 30 seconds to figure out it's what I need. A bazillion thanks to commenters.