There has been a big issue with FindmyPast's Scottish censuses over the last while - it's source citation info on the UK site is occasionally poor, with references such as 644/1 occasionally being rendered as 6441, and with irritating gaffs such as using terminology used to describe English and Welsh returns, as sourced from and catalogued by the National Archives, to describe Scottish records - but with the overseas version of FMP (US, Ireland and Australasia) the references are complete gobbledigook, bizarrely citing non-existent Scottish RG numbers.
An example is with my 2 x gt grandfather William H Paton in 1871, located at Blackford, Perthshire. The source for his entry:
i) According to FMP.com (US): "Archive Reference RG10, enumeration district 2". Huh?
ii) According to FMP.co.uk (UK) "Piece 333, Folio 2, page 16" - Scottish censuses don't use folio numbers and pieces for their citation.
iii) According to Ancestry - "Registration number 333, ED 2, page 16, line 1" - The correct description is almost given here, except 'registration number' should be 'registration district' - but beyond that, a much better effort than FMP.
Transcripts on Ancestry are definitely duff though, and tend to be better on FMP, but you can still find poor transcriptions on both. In the above example again, William's birth place on FMP is given as "West Church Porth"; on Ancestry it is brilliantly noted as "Ka??ch Perth, Perthshire". It is actually West Church, Perth. And that's why it is worth paying to see the original on ScotlandsPeople, or on microfilm, where possible. All are on microfilm up to 1901 - 1911 is not on microfilm, it was only digitally imaged.
You'll also find Scottish censuses from 1841-1891 on FamilySearch, as Peter says, but they are next to useless to use - limited info is presented and it is difficult to locate who else is in the same household. The source info is limited also - you get the Registration District name and the county (so for the above, Blackford, Perthshire), and a GS number, which is a Genealogical Society of Utah microfilm number. The citation given by FS at the bottom of the entry is as follows:
"Scotland Census, 1871,"index,
FamilySearch 
accessed 13 Mar 2014), William H Paton, Blackford, Perthshire, Scotland; citing "1871 England, Scotland & Wales census," index,
findmypast.co.uk( : Brightsolid, 2012.);
PRO T 1, p. 16, New Register House, Edinburgh; FHL microfilm 104072"
Again, that looks duff to me, as I think PRO refers to the Public Record Office, the old name for the National Archives at Kew, but it does give the page number in addition to the above (not sure what T1 refers to), and does say the material has been obtained from New Register House in Edinburgh, where the National Records of Scotland is based (formerly the National Archives of Scotland, and before that known as the Scottish Record Office).
The LDS CD data transcripts from 1881 do exist in database format on ScotlandsPeople (where household entries are only a credit to view) - and also once very briefly on the FamilySearch itself. They mistakenly uploaded the data into their English and Welsh census collection in 2011, and removed it just as quick! (see
here).