Teacher Tapp
I wish that every single teacher in the UK downloads Teacher Tapp and tries to complete the daily survey whenever they remember. I think it is our best way of getting our voice heard. Data speaks loud and clear and cannot be ignored, the more involved the more data there is. They also offer a quick daily read and money off books vouchers. It's a great deal!
Online Stopwatch
I have used Online Stopwatch for years now. It always slightly surprises me when another teacher sees me use it and asks about it having no idea it existed! It is quite literally part of the reason I decided to make this website. You can download the stopwatch from the video and then pin it to your desktop just like I have. It can then run over presentations.
iLovePDF
I use iLovePDF pretty regularly (although slightly less now I am working somewhere that buys the whole adobe suit). If you wish to merge or split or convert anything in terms of PDFs this is my go-to website. There are probably plenty of others, I found this one first, it worked and I haven't looked back.
tiny.cc
Particularly during online teaching, but also at times to display a link on the board, it can be very helpful to shorten links. The website I have always used for this is 'tiny.cc'. There are many other similar websites out there, but I've never gone anywhere else, this one does the job for me.
Classroomscreen
Classroomscreen is a great site that you can sign up to for free. The video from their YouTube here is a few years out of date and misses one of the most important features now available which is the embed function. All your presentations can likely be embedded straight onto classroom screen, meaning you can run your presentation and then overlay all their tools on top!