Right now, you can create communities from

1. https://zapddit.com created by me

2. https://nostr.kiwi created by nostr:npub1alpha9l6f7kk08jxfdaxrpqqnd7vwcz6e6cvtattgexjhxr2vrcqk86dsn

Finding communities is not a perfect mechanism right now. All community clients currently show all communities known, optionally allowing you to pick a community by searching the already downloaded communities.

I suppose all clients will come up with a relay-side search for communities soon.

In fact, expect any community related work to change as it is less than a month-old spec in nostr