Any.DO:

Price: Free, USD 2.99/month for premium features

With the Any.do web app you can easily sync your tasks from your mobile to your home computer. Our extension is also available for Chrome users and allows a quick shortcut to manage your tasks right from the browser. With Any.do reminders you'll never forget to do the things you wanted to, at the right place or time. Any.do works perfectly with Cal, so you can see your tasks right inside your calendar. Cal is a new beautiful calendar. It's fun & easy to create events with the people you care about. It also supports speech recognition so you can dictate task lists.

IFTTT:

Price: Free

IF lets you create powerful connections with one simple statement 'if this then that'. It works through instructions known as 'Recipes' that help you automate tasks. You can create your own recipe or browse through popular ones created by other users. You can add invoices from your emails and  helps in saving your Facebook photos to Dropbox.

Evernote:

Price: Free, USD 4.99/month for premium

From short lists to lengthy research, no matter what form your writing takes, Evernote keeps you focused on moving those ideas from inspiration to completion. Evernote is one of the most popular note-taking app.The paid version of the app offers offline access to all notebooks, a better search experience, a PIN lock and ability to add high resolution images to your notes.

Clear:

Price: USD 4.99, USD 9.99

Untangle your life with Clear - the to-do and reminders app that ensures you stay focused on what matters. Clear’s playful and clutter-free interface makes it easier than ever to stay organized. Once you start organizing your life with Clear you’ll wonder how you ever managed without it. Personalize your Clear lists with themes and make them your own. Simple gesture-based design that allows you to focus.

Inbox By Gmail:

Price: Free

Your email inbox should help you live and work better, but instead it often buries the important stuff and creates more stress than it relieves. Inbox, built by the Gmail team, keeps things organized and helps you get back to what matters. Similar messages are bundled together so you can deal with them all at once. Snooze emails and Reminders to come back when you are ready to deal with them: next week, when you get home, or whenever you choose.

Trello:

Price: Free

Whether you're managing a team of freelancers, writing an epic screenplay, or just making a list of stuff to get done, Trello makes sure you're organized and on top of it all.  It lets you upload files from your PC, Google Drive, Dropbox, Box, and OneDrive.Like a whiteboard with super powers, Trello is simple to use and infinitely flexible. You'll know exactly what needs to get done, who's going to do it, and what's coming up next.