Wired Magazine has published “How to Behave: New Rules for Highly Evolved Humans” which goes a little further than warning you not to tweet/post in all capitals, in fact it goes further than just online behaviour.
I like Don’t Work All The Time, and I try to apply it – but I like what I do and there’s a lot to be done so the temptation to stay and do more is pretty high. Ignore Your Ex on Facebook is logical, although I think I’d extend it to all social media. Meet Online Friends in the Real World, done that and for the most part the people were exactly as I’d expected. It sometimes becomes awkward if you’re trying to explain to real world friends where these random people came from. There’s a helpful guide to choosing a ringtone, and a timely reminder of how our personal space has changed.
The article goes well beyond good manner online – but if you want to assess your online manners try this quiz on netiquette.