Why not use this thread? Here, I'll start with a site we launched last month :)
Site Name: ITS HUB
The ITS Hub is a network for anyone interested in Intelligent Transport (transport technology) in Ukraine. The idea is to connect researchers, innovators, service providers and local authorities etc
See: https://itshub.in.ua 
Setup:
We have a pro licence, the Decorous theme and the Events Map module from AQB soft.
We also created a Ukrainian language pack so it's available in ENG, RU an UKR  ...and we'll make that available via the Market if the UNA team ever respond to our emails ;)
Main Challenges: 
In addition to the language pack (which takes a lot of work) we had to balance the features and decide which options would work best for our needs. Many of the UNA modules overlap or have subtly different features - so you often have many solve each problem. In the end, we decided to keep it simple and use Discussions (for people to talk), Posts (so we can add news) and Events (to list industry events). We didn't add a messenger/chat module or any groups, but might do that if the community grows and we need it.
Funding is also a problem, the pro licence is a monthly subscription which we need to cover until the community can pay for itself (or not) but the UNA Paid Subscriptions module helps with that.

If you have any feedback on the site, any suggestions or recommendations, we would welcome your thoughts....