App 2 SD is another good one. It moves all your apps to the SD card to free up internal storage space.
I recently scanned a 100 page book with Camscanner. It's tedious, but it got the job done. Camscanner has a batch scan option, which sped up the process. After scanning I checked each page for legibility, and only had to rescan 3 or 4 pages. The less motion of the camera the better, and it's best if you can make the page you're scanning as level as possible, which can be difficult with bound pages. There are different settings for scanning quality, with High Enhance being the best and Gray Mode being the weakest. I went with the High Enhance mode, which produced a 19mb file made up of 100 pages. Gray Mode is okay, but it just looks like photos of the pages, and doesn't have the familiar bleached look of a PDF. The High Enhance mode gives you a pretty nice looking PDF.
After I was done scanning the book and creating the PDF I uploaded it to my Dropbox account. I opened it up in Adobe Acrobat, and using the "Recognize Text" tool (which is an OCR), I scanned the PDF to make it searchable.