Hi Sue and welcome to the forum !
we are always really happy to hear about new places to get content. you have some good suggestions already from our members and here are a couple more : for free books, you can make an announcement in our "deals and freebies" forum, and please feel free to add your site to our list of shops in the
wiki with some information about your content.
if you are looking for further distribution options you might also want to make some of your free content available on feedbooks.com ; you can include a link to your site in the book and mention in the description as well where more titles like that can be found. both mobileread and feedbooks get a lot of traffic so both of these are good places to find new readers.
if you are planning to distribute ebooks, i think most people prefer a choice of formats such as epub (the industry standard format) and mobipocket (another popular format for mobile reading devices) which can be downloaded, rather than reading online or pdfs ; do you have plans to support these formats ? you can learn about them here and get lots of advice on how to create ebooks in our workshop forum.
i see in your faq that you are not planning to use drm ; i am really happy to see that you have made this choice ! drm doesn't stop anyone who is determined to make copies, but it does cause a lot of trouble for legitimate customers so it is great to see more and more enlightened publishers dropping it completely.
again, welcome, and please don't hesitate if you have any questions.