I stayed in Ljubljana for a few days when I was there last year, and took a bus to Lake Bled for the day. The city is quite small but very pretty; food and accommodation seemed fairly cheap. The countryside is green and hilly, getting mountainous up towards Austria, and the lakes are nice - Lake Bled is lovely. There's a short coastline with two towns, Portoroz, which is resorty, and Piran, which looks like a mini-Venice. You can visit caves at Postojna (I think there might be others too) and see the Lippizaner horses at Lipice. I don't know much about the inland half of the country around Maribor, though.