Some useful links to get you started (see Learn for dictionaries etc).
The Scots Language Centre is the official source information for all things Scots.
Scots Online is another valuable resource, includes ‘Wir Ain Leid‘ introduction to modern Scots (also in PDF).
Wikipedia has a good section on Modern Scots. The Scots Language Wikipedia is currently being rebuilt.
Scots Language in Education includes a range of materials for schools.
Scots Hoose is a popular resource collection for Scots language teachers.
Itchy Coo is the biggest publisher of books in Scots, especially for bairns.
Luath Press published a range of Scots language books (and Scottish interest books too).
LALLANS – the Scots Language Society publishes the only magazine in Scots.
Oor Vyce is a newish campaign group.