Projectors are great tools for presentations or teaching a group of people, but they are pretty well useless on their own. You will definitely need a screen to project your images on if you are going to be using a projector in public. At home, it doesn't really matter if you use a wall, sheet, ceiling or door, but you will need a professional screen everywhere else. You will also need to use some type of mounting system to hold your slides in place as well as to protect them. There are various types of mounts available for this. You can also speed things up in your presentation by using two or more projectors. If you want to do this, then a dissolve unit will come in handy as it will fade the image from one projector into an image from another unit. Slide mounts can be found for less than a dollar while screens can cost you up to several thousand.