I absolutely love working with Mendeley. It's a wonderful free citing program that has made my life a lot easier.

I am also a big fan of survey monkey. I have only used it a couple of times myself, but I have taken dozens of survey's on this platform and they're clear with lot's of options (question-type options). 

I also love zooniverse, a platform for citizen science. It can be very relaxing to identify some african fauna from pictures, and it's great to think researchers are helped with your contribution. 

And there are so many more options. The tool-database seems like a gold-mine for interesting websites and tools, super handy!

https://www.mendeley.com/?interaction_required=true

https://nl.surveymonkey.com/

https://www.zooniverse.org/projects