Where are good places to demo + share + show off what I'm working on?

1. Create a test suite in a framework of your choice for a practice web page (example: https://the-internet.herokuapp.com/).
2. Share that on social media.

In my city people often meet together to discuss testing topics during meetups.

I've been to presentations on both their testing methodologies and their test automation frameworks. Sometimes they are mixed with presentations for devs, sometimes they are dedicated to testers. You can find a meetup in your neighborhood or organize a new one yourself, using the Meetup platform.

Are you talking about showing off tools, or approaches, ideas, experiences?

I have found the test community full of people wanting to talk about all of those things, but because most of the cool stuff is about ideas rather than a concrete end product there isn't a single repository where people upload stuff.

I find a lot of cool new stuff by following people on Twitter, by looking at sites like http://www.softwaretestingclub.com and by going to meetups and conferences. If I have an idea for something and want to get feedback, then for me what works is using Twitter or posting it on a blog, or going to a discussion forum (like softwaretestingclub, but not here - as this isn't a discussion forum), or going to a meetup. (If there isn't a meetup near you, start one?)

Sharing work stuff is harder as it tends to be confidential. But some organizations do - look at Mozilla or the Wikimedia Foundation, for some examples (I'm finding the WMF QA mailing list a great source of ideas for our automation suite at work right now).

You could also look out for things like Testathon or the Weekend Testers if what you're looking for is to be able to test in public.

Many of the projects we work on will be either confidential or reuse of something that is already created.

In cases where there are valid innovation, they can certainly be uploaded as open-source projects. I think many of the test frameworks or tools that are popular today have started as small utilities and projects that are shared.

You can try sourceforge, github to keep the projects public and receive feedback.