I agree. A list is useful. But to start the thread in a constructive way, I suggest you do a google search and seed the list with pools you find. Then publish the list here and people can add to it. We could also publish the list in the Reddit wiki, alongside the table of GPU hash rates.
Sharing was a feature of Sia, but support for it has been temporarily dropped until (as I understand from the devs) a secure solution is found so that downloaders pay for bandwidth (and not the uploader). So, for now, there is no sharing in Sia.
It could be that a file in your data directory has been corrupted, but as long as you remember your seed you'll be able to access your money. Are you running on Windows, Mac, or Linux?
If you could run the following command from either the Command Line/Terminal and post your results here we can help you get back up and running.
Open a Command Line cmd and cd to your Sia-UI's Sia folder. It will look something like Sia-UI-win32-x64\resources\app\Sia\ . You should see a program called siad there. Run the following command and post the results: siad --sia-directory %APPDATA%/Sia-UI/sia
Did the machine with fewer hosts spend any amount of time offline (like, the machine was running but disconnected from the internet)? I think that if your own machine is offline, it'll start penalizing and removing remote hosts from the hostdb.
Also, is there a big geographic difference between where the two machines are? It could be network instability that's causing you to see fewer hosts.
There may be other causes too. I'm trying to brainstorm potential issues. I'm not sure how good the logging is, but having hostdb.log might help.