If you're looking for fresh reading material for your ereader or tablet, OneHundredFreeEbooks delivers new volumes to you every hour. Search for specific titles, sort by category, or sign up for the site's email list to get notified when new, completely free Kindle ebooks are available to download or when bestsellers get a price cut.
Much like previously mentioned Zero Dollar Books, OneHundredFreeEbooks lets you scroll infinitely to see new bestsellers and other Kindle books that you can download right now for free. If you uncheck "show only free", you'll also see heavily discounted titles.
If the selection you see isn't enough, you can head over to the Deals page to see other discounted Kindle ebooks. Since the site updates with new discounts every hour, you might consider subscribing to the RSS feed to keep an eye on new additions. The site uses Amazon Affiliate referrals, so buying through the site helps keeps it operating.