There ain't much to see in Haarlem, but there are lots of other historical places. If you're interested in seeing buildings I can name good places to see. Each city and place has it's own style of buildings.
If you like green, There is Spaarnwoude in Amsterdam and Amsterdamse Bos (woods)
There is also every year a rally event in Sloterdijk (Amsterdam). Alot other things to do.
Interested in fish? Ijmuiden is the place to be.
Feel free to ask me if you got others question, I've been almost everywhere in Holland