It goes without saying that social media allow teachers to exchange ideas, activities, lesson plans, problems and successes so much more easily than in the past. The opportunity to pick up ideas beyond your own school or department is fabulous and means that no teacher should feel they are working in a vacuum.
Social media forums change over time. The prime platforms form exchanging ideas are currently Facebook and Twitter. In the UK teachers seem to have moved away from other forums such as TES, although the Yahoo group MFL Resources maintains a healthy following with well over 3000 members.
UK-based Facebook groups include Secondary MFL Matters, MFL Resources and Ideas, Secondary MFL in Wales, MFL Teachers, MFL Teachers' Lounge and Languages in Primary Schools. My impression is that the first of these closed groups is becoming to most popular. Teachers on these closed FB groups are courteous and helpful and trolling (which became an issue on TES) seems to be absent. Having attentive moderators helps with this. The same goes for MFL Resources, better for teachers who do not use Facebook and who are happy to receive emails or check digests of email messages.
Twitter has the largest number of teachers and enables you to connect with teachers all around the world. I find it fascinating to read about language teaching issues from other perspectives and even the different language used to talk about the same issues. Twitter can be confusing, however. For one thing, there is no established protocol for the content of tweets. Some "tweachers" post a lot of social chit-chat, mixed with professional tweets. Others stick to the purely professional, whilst others only tweet socially. This means that, if like me, you are most interested in professional tweets, it can mean trawling though a mass of irrelevant tweets. I confess I would like to see more tweets about pedagogical/professional issues. If you are new to twitter you could check out the the hashtags #mfltwitterati (UK based) and #langchat (mainly American).
On Twitter, one useful form of exchange is the Twitter chat, where a topic is chosen, moderated by a teacher and last, say, an hour. American teachers go in for this more often than British, from what I can tell. You tend to find that relatively few teachers take part, although a good deal more may just be lurking and observing. the format is usually very structured, with the moderator asking a series of questions labelled Q1, Q2, Q3 etc, and answers are pre-fixed with A1, A2, A3 etc. Good moderators make sure people stay on topic and remain courteous.
In general the tone of debate between teachers on Twitter is positive and supportive, although the occasional "twitter spats" are observed. This is sometimes hard to avoid when views are strongly held and, to be fair, language teachers are not the most vociferous educators on Twitter. Joe Dale (@joedale) keeps a list of MFL Twitterers for newbies who may want to know who to follow. It's become a cliché to describe Twitter as the biggest staffroom in the world and the best CPD, but there is a lot of truth in the claim. (I say this as a former Twitter sceptic.)
Blogs are another means by which teachers share their ideas and these allow for more detailed descriptions of lessons and pedagogy. Most allow you to leave comments and engage in some dialogue. The borderline between a blog, website and wiki is pretty hazy these days, by the way. Wikis (where you can contribute resources) are quite rare, but you occasionally come across good ones such as the ALL literature wiki. Many teachers use the Wordpress platform to produce their own sites or blogs, others find the free Blogger platform (like this one) simpler for straight blogging. I have a lengthy list of French teacher blogs around the world on frenchteacher.net.
All in all, it's fair to say that it is easier than ever to get new ideas, help and support. But beware, it's all too easy to get addicted! You are almost certainly short of time already, so you may need to pick and choose how to interact online.