Now with Google Maps you can create and share personalized, annotated maps of your world. Mark your favorite places on your map. Draw lines and shapes to highlight paths and areas. Add your own text, photos, and videos. Publish your map to the web. Share your map with friends and family. http://maps.google.com/
Yes, I've just blogged about this one earlier. Looks quite good - I particularly like the way you can publish your maps to the web and share them. Edited to add that there's some demo versions on the site. Check out the Googleplex photo essay.
Do you get the feeling that Google is taking over too many niches? I'm actually quite relieved that they are thinking of moving into paid-for apps, before they give away everything for free and steal all our visitors.