Hi Mathijs, welcome to the forums!
Here are my first thoughts on your site,
http://fun-break.com/ :
* It has an uncluttered layout, which makes it easy to use.
* The aqua page header is OK, but I would remove the square border around the header image (you can do this by putting the image in a separate DIV).
* Your site is unfinished as you say, but it could do with more information on each page. In particular, it would be good if the homepage described the purpose of the site. It's currently not very clear what the site is about.
* I would try to add some unique, original, fresh content in addition to the Google widgets etc. Not only will this encourage people to visit but it's good for SEO too.
Hope that helps!

Let me know if you'd like any more feedback or suggestions.
Cheers,
Matt
--
Matt Doyle, Elated
3rd Edition of my jQuery Mobile book out now! Learn to build mobile web apps. Free sample chapter: http://store.elated.com/