The main bus station is in the city center. It has long distance services from major centers including Shanghai, Hangzhou and Nanjing.
The "Shanghai - Huangshan Scenic Area" long-distance bus goes to Tunxi first, before then continuing to Tangkou. You can drop off in Tunxi. (May 2014)
Tunxi has a domestic airport. The flight to Shanghai Hongqiao is less than one hour. Taxi from the airport to Laojie in downtown Tunxi is ¥30 (2013) which is high for the distance but agreed by the local drivers.
Tunxi has the nearest train station to Huangshan. Confusingly, the station is actually called Huangshan! There is an overnight train from Shanghai (about 13 hours), or Nanjing (about 6 hours) which is far longer than a direct bus, but it does save a night at a hotel, so it is a popular option.