The Meertens Institute has excellent resources for linguistics and dialectology, including dialect atlasses on morphology, phonology and syntax and the Kaartenbank of dialect atlases and maps.
The ‘Kaartenbank’ (database of maps) contains scanned maps of Dutch dialects, including previously unpublished maps from the Meertens Institute Archives. It also includes the recent morphological, phonological and syntactic atlases (MAND, FAND, SAND) as well as the Reeks Nederlandse dialect-atlassen by E. Blancquaert & W.Pée and other 20th century dialect atlases. The maps are searchable by lemma.
The Taylorian holds print copies of the MAND, FAND, SAND. The Bodleian (closed stack) has a complete set of Reeks Nederlandse dialect-atlassen