Go to http://wiipointscard.nintendo-europe.com and select your country. After logging in you can exchange your hard earned stars for Wii Points! They come rather expensive though - 4 stars for 1 Wii Point. So you might want to think twice about spending them, because there's also some cool new items in the Stars Catalogue on the main NoE site.
Regardless, it's still a nice feature and a good incentive for Europeans. After all, why should America and Japan always get the good stuff?