Here is a selection of links to various resources on the study of Scots:
Dictionary of the Scots Language Homepage
Includes searchable versions of the Dictionary of the Older Scottish Tongue (DOST) and the Scottish National Dictionary (SND).
SCOTS Project
Large corpus of texts and speech in Scots.
Scotsgate
Scotsgate has lots of information on all aspects of Scots.
Scotsgate Grammar
Eighteen-page introduction to Scots by C. P. L. Young.