m2eclipse has moved from sonatype to eclipse.
The correct update site is http://download.eclipse.org/technology/m2e/releases/
If this is not working, one possibility is you have an older version of Eclipse (< 3.6). The other - if you see timeout related errors - could be that you are behind a proxy server.
Maven Integration for Eclipse 正确地址
原文：http://www.cnblogs.com/swack/p/5358986.html