When you need something for your current newsletter, go back a couple of months. This avoids the problem of the same article appearing at almost the same time in several ezines. Article libraries are a great source for good material. Here are a couple. You can search for articles by author name or simply select a category.
All articles are available via auto responders, so they are easy to get and they arrive quickly.
IdeaMarketers - Navigation seems a bit tricky, but it is easy to get an article you like. Lists ezines by category and provides useful information about each one listed. This is a must-visit site for all who are looking for better ways to put out an ezine. You will want to set a bookmark and return often. Kate has whole bunches of terrific ideas she wants to share with every visitor.