From the last Tuesday in June (if the blueberries are ripe) till the first Saturday in September you can pick blueberries. You can do that at blueberriefarm De Pollekamp.
There are 8 fields where you can pick your own blueberries. At the reception you will get a bucket from the farm. The people from the reception will tell you which field you can go to and pick the blueberries. Once you arrived at the field, you can go to the row you like to pick them. It is up to you how many you pick. There are people who only pick till the bucket is halfway full. Or you can go till it is completely full. After you are done, you go back to the reception and give the the bucket. They weight it and from there they say how much you have to pay (it goes per kilo).
At 15 July 2011 the price was Euro 3.75 per kilo. But I bet it will go down to the end of the season.
The opening hours are:
Tuesday till Friday 10 am - 5 pm
Saturday 10 am - 3 pm