The new Photos app for Mac allows you to store all of your photos on Apple's servers as part of their iCloud service. This makes your entire Photos library available on all of your Apple devices including Macs, iPads and iPhones. You can add, edit or delete photos on any device and see the changes on all of them. You can choose to store original photo files on a device, or have the device only use optimized versions of the photos. You can also view your Photo Library on iCloud.com.
People ask me about the camera I use to record these tutorials. I have been using the C920 for the last two years and find this inexpensive webcam to be better than some other expensive and more cumbersome solutions. It uses H.264 compression in the camera to allow it to send 1080p video over USB2. It works with any Mac and most apps. See a quality comparison between the C920 and the MacBook's built-in FaceTime HD camera.
You can erase your Mac and set it up so it is ready for a new owner by using the recovery partition. This hidden part of your hard drive allows you to boot into a special mode where you can erase all of the contents on your Mac and re-install the system. There are a few things you should do first, such as logging out of iCloud and deauthorizng your account in iTunes. By using a special security feature of Disk Utility on the recovery partition, you can ensure that your data is erased.