This list changes. It is not exhaustive. That's what Google is for.
These are my top tools:
Save time, search for a prezi presentation someone else has started, make a copy, fix it/finish it/adapt it to your needs. No point re-inventing the wheel.
Get involved with a community of teachers to organize multinational projects.
Reddit divides its content into subreddits. I recommend you search only within subreddits in your area of interest.
This is a way to make QR codes for free. I am currently experimenting with homework assignments using QR codes and even class-based use for cheap augmented reality lessons.
These are some of the tools I use:
You need to make it easy for students and teachers to find you. If you don't have the time to curate a your profile I recommend you don't have one at all.
This is your professional profile and within LinkedIn, there are groups of professionals in ELT around the world who can help you. I belong to three groups: TEFL Institute, English Teachers Anonymous, ESL teachers on languagespirit (pending).
Transparency is increasingly important. Being a teacher has never been more of a public profession than it is today.
These are tools I am looking into:
These are tools I find interesting but don't recommend except for digerati: