This may not be the easiest thing to do, but look for current events that you can connect to your niche. For example, when the Amazon Kindle made some changes, I wrote to my list and told them about it. Then I reminded them of the webinar training I had done to show how to submit your eBooks and short reports for publication by Amazon for Kindle users.
The idea was that my list would be interested in knowing about the Kindle because I teach eBook writing, as well as internet marketing. This was in the news so I jumped on the story and shared it with my list.
Once a month you can do an online search for stories related to your topic. Keep your eyes open all the time, but if you spend one hour every month doing this type of search it will really pay off. This helps to position you as an expert in your field.