Kuna is the official monetary unit in Croatia. The abbreviations are "kn" and "HRK". 1 kuna equals 100 lipa.
The "keeper" of the currency is the Croatian National Bank. See their web pages at http://www.hnb.hr/ for more information on kunas, including pictures of the actual banknotes.
Kuna is officially linked (compared) to the Euro, and currently 1 Euro can be exchanged for around 7.5 kuna (2003).
The word kuna means marten in Croatian, and the word lipa means linden.
This was introduced ten years ago after using other currencies such as crown and dinar for decades and even centuries, so it was a bit hard for the citizens to get accustomed to talking about trading with wild animals and trees. :-)