The first place to turn for help is always the mailing list.
Please don't ask for help by filing tickets in the GitHub issue tracker. Yes, I'll see your ticket, but I'll just ask you to re-post the question to the mailing list. There are some sharp people on the list and you'll get a quicker response that way. I also prefer to use issue trackers for tracking new features and bugs, not support.
You can follow Nesta on Twitter at @nestacms. New themes and plugins, new features, etc. get tweeted.
Feel free to ask questions on Twitter but bear in mind that 140 characters isn't the best medium for support, and that you're only able to get help from one person (who might not be around anyway).
Messages to the mailing list will also be read sooner, by more people, so use that.
The #nesta IRC channel on the freenode network is a great place for us to chat with you if we think a real time conversation will be the fastest way to solve your problem.
If you haven't arranged to meet us in there for a chat, you'll probably find it a bit quiet...