Apple Mac has a lot of options when it comes to applications. One of the things I understood early on is the fact that most of these applications are paid ones and you have to struggle and search if you want to find useful alternatives that are free.
Below are some of these free applications that I found to be useful.
AppCleaner - When you install applications, the files are distributed across the file system. Now while you uninstall that program, it doesn't remove all the files from all locations. This nifty application shows you all the related files which you could clean out easily.
ImageOptim - as the name suggests, you can drag and drop your images and it reduces the file sizes considerably by invoking advanced compression logic. It also helps remove/scrub the associated data like EXIF which is not needed at times. For bloggers, it serves two purposes. Less storage on your hosting client and quicker load times on browsers, since the size is small.
Clean-Me - is another nifty program that helps clean your Mac. When it comes to maintenance Mac already does a good job compared to Windows. However, once in a while you need to clean, purge the unwanted logs and caches. This tool helps you do that with a click.
Latest - all the applications that are installed from the Apple store can be updated with a single click. We install a lot of applications from other websites as well. This app would take care of updating all your applications to their latest version from a small UI itself.
Dropzone - this is a great application to move or copy your files. It helps you to copy your files to different folders, different services, etc. Like, say you have a file on your desktop and you want to copy that to your Google Drive, drag & drop would achieve that.
Clocker - do you work for an MNC having offices in different time zones or you have relatives across the world. This is a nice app to show you different times at different time zones.
Handbrake - do you need to convert video files to different formats? If so, this tool can help you do that. If you want to convert that MKV file to MP4 so that you can still play on your old TV, this could help.
Download Shuttle - This is the download accelerator for Mac. It splits the stream and downloads into different segments. You could pause and resume the downloads as you please.
Padbury Clock - Absolutely gorgeous screensaver for Mac. It displays time in a black background and it is mesmerizing to watch.
Grammarly For Safari - The must-have app to make sure you are not making mistakes on the grammar front. The free version does help and I use it a lot.