If you make presentations to small audiences in rooms where you can turn the lights down, there is a 500 lumens DLP projector that you should consider, it is the K330 DLP LED 3D Ready Projector from Acer. At only 2.7 pounds (1.2kg), the K330 is portable, inexpensive, and comes with its own carrying pouch. Along with video and computer inputs, the K330 also sports an HDMI input for connection to digital sources that you may have access to at your presentation. You will be surprised at what a good image you get from such a small projector, and that is a strong point for the K330.
For less formal settings, the K330 performs well for family gatherings where viewing home movies or pictures from a recent vacation are the focus of the evening. It is compatible with personal devices like iPods and iPhones, and it has both SD and USB inputs which can display stored images from memory cards and thumb drives. This input versatility is uncommon in pocket projectors, and it virtually eliminates the need to have a computer connected to enjoy using the K330.