Mochi is a flashcard app that uses Markdown and has Mac/iOS/iPad/Web versions. It has a bunch of keyboard shortcuts and supports neat stuff like pasting images right in, LaTeX, and syntax highlighting.
FreeCodeCamp has free coding exercises/certifications in various areas that you can use in-browser.
I plan to add more to this topic over time.
I like Flexcil:
The pop up document feature is good for letting you have notes/scratch paper floating “on top” of a PDF while letting you get the pop up out of the way when you don’t want it anymore. You can also have a PDF as a pop up for looking at a solutions manual. Imho it’s nicer to have PDF viewer plus notes/scratch paper in same app rather than needing to do split screen with multiple apps.
http://Otter.ai is a great and cheap computerized transcription service that makes transcripts from audio and video files you upload. You can use it as part of your learning process to make transcripts of non-text resources that you can paste from and discuss. The transcripts it makes are also searchable and clickable on their website so you can use it to find and listen to particular points in a big lecture quickly.
A number of things on this page I made a while back are relevant, especially the Reading & Listening and Videos stuff, along with the Dictionaries
Thanks @JustinCEO for finding Recut, a Mac app for auto silence removal from videos or audio: https://getrecut.com (btw the price is going up from $29 to $99 on Friday)
Another option for automatic silence removal is https://www.descript.com The main feature of Descript is that you can edit a text transcript and it’ll edit the video or audio file for you.
If you want to talk about something and then put up a recording for other people to hear, automatic silence removal may be for you!
Happy to help!
BTW, having used both Recut and Descript, one thing I’ll note that is that Recut is, IMHO, much much better suited than Descript for workflows where you’re recording a ton of material where there will be long silences. Descript has caps for hours you can transcribe in their membership tiers, and they calculate your hours used by the length of the initial file uploaded, and you can’t remove silence using Descript until after the transcription is made, so, yeah, use Recut for that case (at least for the initial rough cut and then you could use Descript for finishing touches)
I’ve never done really long silences in videos – not more than a couple minutes of thinking. Do you do them often? What for?
Wait, I’m wrong, yes i have. I’ve done long silences when writing. I was thinking of videos focused on me talking, but I’ve also e.g. streamed me writing an article without talking much.
I did on a couple of recent vids cuz I was spending time reading stuff, looking stuff up, and just let the recording run and removed the silence on the backend. It was good to just not have to worry about whether I’d turned the recording back on or not. More natural
Doesn’t your mic pick up some mouse clicks and typing during the silences?
I think I have a bunch of stuff that helps minimize that from happening.
so then assuming clicking or typing gets through all that and I’m using Recut, the sound still has to 1) exceed the threshold for what counts as silence and 2) be longer than whatever this is set to
I haven’t carefully reviewed my own recent videos tho, so might be more of an issue there than i am aware of
Calibre’s content server is pretty useful and easy to set up. Calibre is ebook management software. The content server feature lets you share a collection of ebooks across your home network (or even the internet). If you set up a user account, you can access and add books to your calibre library from anywhere on your home network. Pretty nifty. 
It seems like you wanna use their tools (such as content server) cuz if you try to rig something up using e.g. Dropbox and running different installations of Calibre on multiple computers, you may run into database problems and issues with keeping everything in sync
the iOS client for the email service I use, FastMail, has a “Share Message Content” feature that lets you easily send the content of a message to another app (like Voice Dream Reader). Pretty handy
I haven’t checked it out and so can’t directly speak to its quality, but the Ayn Rand Institute has made a book version of Leonard Peikoff’s grammar course available: https://www.amazon.com/Principles-Grammar-Leonard-Peikoff-ebook/dp/B08Q2J7QKN/
I went through the course in the only format it was previously available in (audio lectures + handouts). You can find the lectures and handouts free online. I enjoyed the course and recommend it if you are interested in grammar. If someone tries the book, lemme know what you think of it.
This app is a simple epub viewer with no “library/bookshelf” type of function. It’s just like Preview but for epubs. Notably, when I open an epub in it, and paste the contents to this forum, at least some formatting (e.g. bold) pastes in correctly, which is nice.
I’m hesitant to recommend it cuz it is a paid app that hasn’t been updated in 3 years and I don’t know if it’s under active development (kind of assume not at this point?), but it fulfills a kind of underserved niche so it seemed worth at least a mention.
you can make quizzes (including multiple choice and true false) in text and then convert them to a standardized format using this program:
this website lets you make a free account (you can say you are Evaluating/Other) and you can import quizzes you make with text2qti to it.