hey, One method you can use to find some blogs on your niche that might take Guest Posts is by doing a simple Google Search like this... "guest post" + "powered by wordpress" + "your specific niche keyword here" this is to find other WordPress Blogs of course. If you are looking for just any blogs I would suggest using the search engines to find other blogs in your niche and simply Contacting the Owners and ask them if they would accept a guest post from you. Remember to be ready to show some of your Writing Skills with your previous writing work - some people might ask to see how you write and what kind of posts you create before letting you publish on their blog. You can also use the same search structure to find other WordPress blogs that have a Contact Page so you can contact the owner. Try to get creative when looking for ways to find good sites for Guest Posting. Hope this helps! Wish you much success!
Close friend of mine created this list: http://nancybadillo.com/sites-that-allow-guest-posting/ It is very similar to one I made. She kinda steal the idea but it is a great list still. Just remember than 90% of the blogs from this list don't accept posts automatically. You will have to pass some certain tests. Good Luck! Hope I helped!
You can ask Google for guest post sites, if you not satisfy with the Google result then PM me for even better result..