The list compiled here is really nice and the criteria is quite helpful. I have used them all and I can say that they are good. A couple of days ago I have discovered a new web page, a friend of mine recommended it to me and I saw that it is actually good. I have posted some answers on it, it is ask.whatafy.com, it sure is loads of fun. It is relatively new, but there are interesting pieces of information hidden there. Has anyone heard about it?