Guru Nanak spoke of one religion and through his life was a true example of an universal being. Where ever he travelled, he took on the form of his surroundings, preaching the same message, but in the language of the local people. He was also known to perform many miracles. When you read his teachings you see clearly that he is speaking of vibrations, of the paramchaitanya.
In Sahaja Yoga we know Guru Nanak as one of the ten Primordial Masters.
Additionally Guru Nanak is known as the founder of the Sikh religion. Sikh actually means to learn. The Guru Granth Sahib which is the holy book of the Sikh religion contains much of the teachings of Guru Nanak, as well as those of earlier saints such as Kabir and Namdev.( Mohan)
Guru Nanak's Birthday 1999 Delhi
Guru Nanak's Birthday 1982 London
Guru Nanak's Birthday 2008 Delhi (report and video)
Guru Nanak and Sahaja