The scottish-folk-music.com site is better, but still depends on those in the clubs and sessions submitting updated info to the administrator of the site to keep it up-to-date.

However, there is now an absolute plethora of Facebook sites on which people advertise their gigs, sessions (see the same gig ad 10 times in one day?) etc. Just do a search on "groups" in Facebook, nominating folk music as your interest and you'll be deluged with potential groups and pages to join! Here are a few for starters:
Scottish Folk Music
What the Folk's Up
Houseconcerts in Scotland
Fiddles in Scotland
And most folk clubs have their own FB groups now.