Custom labels for Google or whatever
Just one interesting idea 
It would be cool if users could change the texts of links in their accounts for example in Google Mail or whereever.
It will be really fun and I think many will like it. You can change the labels of menu items to everything you wish (Incoming->rcvdMail, Pictures->Pix, Friends->Dudes, My Profile->Ma Face, Yes->YEP!, No->NAH!) and then you can save all changes in special format (XML file) and you can share it with your friends.