That would be a very nice time to be in Haarlem then.
It's the main shopping town for the area, and it's gets crazy fun on Thursday nights with late shopping night, everyone is out and walking around, and the majority of the downtown core is walking streets only.
Some recommendations:
The market on Saturday is wonderful, and you can really Rick Steves/ETBD style travel there by grabbing stuff for a picnic. There also seems to be a bakery, and cheese store every few feet. hehe
The Bavo Kerk in the main square does Sunday mass, and has one of the most incredible pipe organs in all of Europe, if that's your thing: http://www.bavo.nl/bladen/welkomkerk.htm. I've also found it to be one of my favorite cathedrals.
The Hiding Place is a touching place to visit, with a story almost as powerful as Anne Frank's. http://www.corrietenboom.com/index.html It is run by very proactive born again christians, so there is active missioning on the tour (if that's not your thing), but it's a powerful experience.
There's an incredible ice cream shop down Klein Heillighland.
AND - Amsterdam is only 15 mins away. LOL So there's no real need to miss anything there. :)
Rick's also got some great suggestions for other thing s in Haarlem. I used to live there, so don't know a tonne about the tourist(y) stuff. But I hope that all gave you some food for thought! :) Chris