Official site, for modern stamp issues of Malaysia.
The Malaya Study Group exists for collectors of the stamps, postal stationery and postal history of the states of Peninsular Malaysia which until 1963 formed the Federation of Malaya, including the Straits Settlements of Malacca, Penang and Singapore, the Federated Malay States, Negri Sembilan and Sungei Ujong, Pahang, Perak and Selangor and the Unfederated States, Johor, Kedah, Kelantan, Perlis and Trengganu.
The Sarawak Specialists' Society was founded in 1947 to further the study of the Stamps and Postal History of Sarawak, Brunei, North Borneo (Sabah) and Labuan.The site provides useful information about the philately of these states.
Wikipedia page providing a useful introduction to Malaysian philately.
Recent news about Malaysia stamps, from StampNews.com.