Knowledge of foreign languages in the Netherlands, in percent of the population over 15, 2006. Data taken from an EU survey. ebs_243_en.pdf (europa.eu)
Knowledge of the German language in the Netherlands, 2005. According to the Eurobarometer:  70% of the respondents indicated that they know German well enough to have a conversation. Of these 12% (per cent, not percentage points) reported a very good knowledge of the language whereas 22% had a good knowledge and 43% basic German skills.
Another Low Franconian dialect granted the status of regional language is Limburgish, which is spoken in the south-eastern province of Limburg. Limburgish is spoken by 825,000 speakers. Though there are movements to have Limburgish recognized as an official language (meeting with varying amounts of success,) it is important to note that Limburgish in fact consists of a large number of differing dialects that share some common aspects, but are quite different. 
West Frisian is an official language in the Dutch province of Friesland (Fryslân in West Frisian). The government of the Frisian province is bilingual. Since 1996 Frisian has been recognised as an official minority language in the Netherlands under the European Charter for Regional or Minority Languages, although it had been recognised by the Dutch government as the second state language (tweede rijkstaal), with official status in Friesland, since the 1950s.
Luxembourgish is divided into Moselle Luxembourgish, West Luxembourgish, East Luxembourgish, North Luxembourgish and City Luxembourgish. The Oïl dialects in the Benelux are Walloon (divided into West Walloon, Central Walloon, East Walloon and South Walloon), Lorrain (including Gaumais), Champenois and Picard (including Tournaisis).