I'm interested in lists of usernames by service (this could be useful, for example, for making username generators). So far, the best thing I've found is this:

https://github.com/notwa/twitch_usernames

I know there's a reddit comment database, but it's 250 GB and I just really want the set of unique usernames for it. If anyone could host that, I'd be quite interested.

Other services that might be interesting:

- Wikipedia
- Github
- Twitter
- Youtube
- Tumblr
- Services whose primary user interface is *not* English.

Mainly I just want the usernames, but if it also has other data (like gender or age breakdowns), that would be fine as well.