Please reply with just one blog per answer to allow the voting system to bring the best/most popular to the top.
Even if you don't listen to The Java Posse then reading the blog is great for a regular summary of what's happening in the Java world. But you should listen to the podcast :)
http://www.theserverside.com/ is pretty good for JEE articles.
For Java and a few others, anything by Bruce Eckel is going to be worth reading.
http://www.infoq.com/, http://www.dzone.com/, http://www.javablogs.com/, http://www.jroller.com/ and http://www.theserverside.com/ among many many others. The sites listed above aren't individual blogs but a group of aggregators with user submitted content.
If you read french check http://touilleur-express.fr A very good blog in french about java.
Dan Dyer's New Adventures in Software is a great blog with quite a lot of Java content.
I don't want to duplicate infomation too much (DRY and all :), so see this answer for a few more sentences about the virtues of the blog.
Core Java Tech Tips For in depth coverage on Java features (though updated less frequently)
I got a lot of my java dose from http://java.dzone.com (previously Javalobby.org)
https://www.ibm.com/developerworks/java/
I especially loves articles from Brian Goetz
http://www.mastertheboss.com has got plenty of tutorials about JBoss Hibernate Java EE technology.