Apple computer prices are pretty much standart across online retailers. Assuming you are from USA, the best places are Amazon, BHphotovideo, bestbuy or Macmall
http://www.appleinsider.com/mac_price_guide/
the MacMini will be the right choice for you I believe, its the cheapest entry. Altough you may use your display, keyboard and mouse, you have to get the apple magic mouse in order to get a full experience. Also, later on, go to macsales.com and order 8GB of memory, its less then $50