Caithness Parish and Probate Records 9,900 records including baptisms/christenings, burials, marriages, tombstone inscriptions, obituaries, tax lists and wills
Caithness Marriages 19thC at Williamson Genealogy
Caithness, Orkney and Shetland Births, Deaths and Marriages
Caithness.org Forums - Births, Marriages and Deaths posts at this forum include recent Caithness marriages
Scotland Births Deaths and Marriages Exchange over 80,000 records
ScotlandsPeople.gov.uk -  Marriages 1553-1928 (small fee) a partnership between the General Register Office for Scotland and Scotland OnLine that has nearly 40 million online records including marriages from 1553-1928