There is no cheat sheet about elgg on http://www.cheat-sheets.org/
Do you know if there is one ?
I just uploaded a cheatsheet for elgg 1.8, maybe what you were looking for
I had nothing better to do despite my 16 hour days ;-) and so I am working on a techie cheat sheet for Elgg core API functions reference - similar to the (DoxyGen) API documentation available via http://elgg.org/developers.php -- but a summary of the Elgg core code classes, functions in a easy to browse single document listing.
Hopefully - this might turn out to of some good use - esp for the techie folks - of course you gotta be an Elgg coder if you wanna put this to some use ;-O
Will I actually finish this, another of my wish-list tasks, which sometimes I cannot find time to get done ?
Weell... kinda, also depends on interest feedback re: whether people will actually welcome such an artifact and would want to benefit/ put to daily use, etc, etc ad nauseum.