For international travel, a good place to start might be fromatob.com, a price comparison website which tracks various means of transport to find the cheapest and fastest means of travel. Whatshalfway.com is also an innovative website which gives a midway meeting point between two different locations.
Within the Netherlands, 9292.nl is the best journey planner for public transport. You fill in where you need to go and they will tell you how to get there the quickest using bus, train or both. You can also try the tool provided by Arriva Transport or the NS journey planner. Bear in mind, however, that the NS journey planner doesn’t include buses. To find a bus stop near you, check this map for an overview of the Arriva bus stops in Maastricht, and this PDF shows the network of Arriva buses and trains in Maastricht and Limburg.