Valuable info from the comments
The problem with putting some valuable information into community memories is that one cannot add comments to memories, only entire posts. Some really valuable information that deserves to stay in our archives literally slips into sand this way - because the commenting threads can lead quite far from the subject of the initial post. I remember an excellent definition of different types of Russian reflexive verbs (given by yms several weeks ago in coments to somebody's post,) but could not find it recently - because it wasn't in the community memories, and there was no way to put it there.

So I'd like to start a post that we could update from time to time, with some more or less valuable grammatical, lexical etc. information that would be otherwise lost in numerous comments. Please add comments to this post if you are suggesting a new piece of information has to be added to it, providing the link to the comment you regard as worth of archivation. I will then add new categories to its description in Memories section.
The link to this post will be added to the Community Info, so that we won't lose it :)

Here's my initial two kopecks:
Russian prepositions в/на vs. English on/at/in: some usage hints
Seven types of Russian reflective verbs (the verbs that end with -ся)