Removing backgrounds from photos can be a little tedious, but if you get the right background you can do it really easily. Fortunately, your computer's display can be a quick-and-dirty tool for creating photos with easily removable backgrounds.
The process is really very simple. Pick something you want to take a picture of and remove its background that's smaller than your computer screen. (Those of you with large displays will obviously have an advantage here, but I use my 13-inch laptop all the time and it works fine.) Then fill the entire screen with green, white, or some colour that will contrast nicely against the subject of the photo. There are a lot of ways you can fill your entire screen with colour, but the method will depend on your image viewer. If you've got Photoshop, you can simple make a new document, fill it with a colour, enter full screen mode (just press F twice) and zoom in until the colour fills the entire screen.
Now place the subject in front of the computer screen and take the photo. When you bring this photo into your image editor, you can quickly knock out the background by using the magic wand tool. Generally the magic wand isn't very good at removing backgrounds, but since you have an even colour behind your subject it can select the background very easily. All you have to do is use it to select the background and delete the selection. Now you have a background-free photo.
One thing you should be aware of is that your screen is backlit, so you want to make sure there's adequate light on the subject of the photo or you'll end up with an underexposed subject. This is generally pretty easy to do by just moving in front of a window or putting a lamp in front of the subject. While this method is never going to be an ideal way to remove backgrounds, if you need to do it quickly it's very useful. I often have to create fairly complex graphics in 10-20 minutes for Lifehacker posts (like this) so I use this trick a lot. Though imperfect, it works pretty well for a lot of things, so next time you need to knock out a background it's a good option to keep in mind.