There's a train that goes into Mariestad, but it is also served by bus; car always works!
The biggest sweetwater lake in Europe, nice boating, and supposedly a lot of Swedish tourists in summer.
Go swimming, rent a bike, or have some other fun. On Saturdays, there's a market at the main square
There's a fine coffeeshop with great blueberry-vanilla sauce cakes, right at the main street. The Pizzaria can not really be recommended, but it's cheap and ok food