No EUR yet
Czech Republic joined EU in May 2004.
The local currency is CZK (Czech Koruna) or ceska koruna.
It is freely convertible, currently around 23 korunas for 1 USD or 18 korunas for 1 CAD.
Whenever I go there, I use banking machines for withdrawals conveniently located everywhere. The exchange rate seems to be better as well.
Beware of pickpockets in the Prague centre, use common sense and you'll be fine.
Enjoy!