Folk museum is just feet away from glamis castle. From the entrance at the main driveway it is just round the corner and from the other exit of glamis you walk by it so there is no reason not to take a look. Basically its a museum about life in bygone days. The museum is 6 white cottages all joined together and across from it is an exhibition of machinery used in rural times. There is an entrance fee (can't recall exactly, think it was between £5-£6 but may be wrong). It is a small museum but it is also very interesting and they have tried to pack a lot into the space. It won't take a huge amount of time to view, an hour (maybe less) but its worth a look. Take a look at the castle then pop into the folk museum (closes 4 30pm) (If doing castle and museum might need to go to museum first then castle (castle closes 6pm but it takes a while to view it and the grounds, but that then a 20 - 25 minute walk up the driveway to the castle entrance doing it that way) If taking public bus check timetable carefully, buses to glamis and back fairly long inbetween, don't run that regularly.

Travelling back from holiday we noticed signs to this small Scottish Trust property. The property is split in to two. One part is a series of cottages showing an insight in rural home life, the other part, which is across a small road, displays agricultural machinery showing the working life of the people. The whole collection is the result of one person.
Well worth a visit. Allow around two hours to see everything. Enthusiastic staff are able to answer any of your questions.
For National Trust members the museum is free, for others a fee is chargeable.