Cropping images can be a huge pain if you have a bunch to do at once. Even if you have Photoshop or a similar program, the process of opening each individual photo and cropping them one at a time can take forever. A free web-app called Cropp.me makes that task a lot easier by auto-cropping your photos to whatever size you choose.
All you have to do is upload an image, choose what size you want it to be, and click Cropp My Images. You can choose from a list of sizes or input a custom size of your own. It looks for the most "visually interesting" part of the image and decides where to crop it based on that, but you can adjust it as much as you want. One of the coolest features that Cropp.me offers is the ability to upload up to five images at a time and batch crop them and download them as a .zip file.
Once you're done cropping, you can download your images and throw out the ones you don't want, all without ever creating an account or downloading anything. It is possible to use Cropp.me to make images larger, but it's meant to only be a cropping tool so it depends on how picky you are about the resolution. It's also worth noting that if you upload an image with 300 pixels per inch, it will drop down to the standard 72 pixels per inch.