Regular Cercanías trains to Aranjuéz travel from Madrid's Atocha railway station; buses leave from Estación del Sur de autobuses. By car Aranjuéz is reached by taking the N-IV (carretera de Andalucia) south from the city.
The first thing one notices when approaching Aranjuéz is its lush greenery, in sharp contrast to the surrounding arid landscape. The principal points of interest here are the 18th century "Palacio Real" (Royal palace), the "Casa del Labrador" (the labourer's cottage) and some exceptionally fine gardens, especially the "Jardin del Príncipe" (Prince's Gardens).
Since Aranjuéz lies about halfway between Madrid and Toledo, one might consider making a single outing from Madrid to visit both sites.
Oficial website: http://www.aranjuez.net/