The Kindle is great for reading, but it's horrible for research. If you need to bounce back and forth between pages for comparison, it has always been a bit of a pain. Page Flip is a new feature rolling out to the Kindle apps and ereaders that should help. The new feature's described as the "digital equivalent of sticking your fingers in a book", and is most clearly useful for non-fiction books where you find yourself bouncing between glossaries, endnotes and references. Once you pull up the Page Flip view, you can easily find a page, check out a bit of information, then bounce right back to the page you were reading before. The feature is book-specific though, so you'll have to look for "Page Flip: Enabled" on the Amazon store page to make sure it's enabled for the book you're reading. The update's available for all the Kindle apps right now, and should be rolling out to Kindle devices with an over-the-air update.
Page Flip [Amazon]