You absolutely have to learn to think outside the box if you want to get the best possible results from your PLR content. You'll only get the most leverage from PLR when you're using it in a way that everyone else isn't using it. One great idea is to use PLR content as Twitter tweets. Your informative tweets can really be used to help you get the most of the niche-specific and rather large following you've taken great pains to build. You can handpick the best points that you feel would be worth sharing, and tweet away - as simple as that.
You might also want to think about using PLR to answer forum questions that have to do with your niche. People are always looking for advice they can put to work right away on forums and you can use PLR to give it to them.
Let's say that your niche is related to dog training and you have tips for training various breeds among your PLR collection. The trick is to join several niche specific forums and provide content from your PLR whenever it's appropriate to do so. This will help establish you as an authority on the topic in addition to gaining you new traffic as your posts gain interest and people click on your links.
Build an article directory that is specifically for your niche. You might find a wide range of article directories online but you're not likely to find very many that are dedicated to only one niche. One way to do this would be to buy a bunch of PLR articles in a niche like weight loss and then create an article directory where you could post all of these weight loss related articles. Keep in mind that bigger is better with directories so make sure you allow other people to post their weight loss articles in your directory too. Once you've amassed a huge collection of content you may even consider selling your directory. If you've been using AdSense on the site to generate revenue you may be able to sell it for quite a bit of money.
Try to target new markets by translating your PLR content into another language and selling it as an eBook. This type of "outside the box" type of thinking will get you even more profit from your PLR. You need to make sure you keep popular languages like German and French in mind for this purpose. It's the differences in the way you use PLR that set you apart so don't be afraid to try something new. You need to use PLR in an effective manner if you really want to grow your online business. These ideas are fairly simple to implement so use them well.