Well it's that time of year again in Scotland when we have the nominations for the MG ALBA Scottish Trad Awards open until 22nd October, and this includes a category for Event of the Year - which could well be your favourite Scottish festivals - up to 4 nominations allowed. See here how to nominate: http://www.handsupfortrad.co.uk/tradmusicawards/index.htm
My favourite Scottish festivals include Celtic Connections (Glasgow Jan-Feb), Girvan, Glenfarg, Stonehaven, Innerleithen, Auchtermuchty and Dougie Maclean's Perthshire Amber (Oct - Nov) and of course top of the list is LINLITHGOW (which I help to organise - not in the least biased, of course!!)
See here for some of the fun we had this year: http://www.linlithgowfolk.com/festival.htm
and the pics and videos:

http://linlithgowfolkfestivalphotos.shutterfly.com/2010folkfestival