About sights in Ljubljana: there is a castle with great virtual museum (without European Youth Card discount), there are cafes by the river and you can take a boat trip (European Youth Card discount), there are museums (museums with European Youth Card discount) and tourist sights (some with European Youth Card discount) worth visiting. In August the TRNFEST festival takes place in Ljubljana with free music and theatre. More information: www.visitljubljana.si.
The only camping site in Ljubljana is Camping Je¾ica (www.ljubljanaresort.si), it's a few km outside the centre. You can also stay at the hostel in the centre and near the train station, called CELICA - THE CELL (it is really interesting designed - from 16 - 27 EUR per night - www.hostelcelica.com)
Cheap accomodation with European Youth Card discount: hostels, hotels and guesthouses.