I've started an online database of .NET User Groups around the world at www.DotNetUserGroups.com. The Twitter handle @DotNetUsers.
It's a little bit like the official one (https://www.meetup.com/pro/dotnet/) but less geared towards meetups and more towards meeting some of the other needs of user groups.
It's at its early stages at the moment as I need to do a massive data cleanse and well.. generally make it better.
If you feel like helping out with this side project, please get in touch. It's still early days.