Links to currently usable sites:
A website for determining how best to brew a cup of coffee.
A website for playing D&D solo or just winging it when feeling to lazy to DM a proper campaign.
If you're already using the site XMPP server and need client recomendations, below are the options I'm personally using and working to support.
Best browser XMPP client I've used so far. There's definitely some bugs, but largely it works better than the Xabber web client.
Hands down the best Android XMPP client, while you do pay $3 for it on the Play Store it is open source and you can find it on F-Droid for free.
Using GTK, it's not nearly as pretty as something like Telegram, but offering about as much control as any PC XMPP client can, it's been the best featured and most reliable I've used so far.