The Holland Festival is on! Despite their not-so-great website, this is an event definitely worth checking out. I found some great information over at Holland.com that should help to convince you:

Since 1947 the Holland Festival has been the trend-setting performing arts festival of Holland. The festival is a mixture of performing arts, theatre, music theatre, dance, opera and music, and visual arts, literature and architecture. What makes the Holland Festival unique is the fact that it always tries to renew itself. Every year you'll be surprised by daring experiments and trend-setting performances presented at the international level.

Do check out the official site for detailed info about what's on when and where.